Forerunner 255 Series - Recent Threads

Firmware (gupdate.gsp) - 255s Music

Zrody — Wed, 23 Sep 2026 22:57:18 GMT

Hi, I need an old firmware for teh 255s Music (the s version).

Thanks.

Oscilação do pace

Érica Franco — Mon, 21 Sep 2026 20:03:21 GMT

Tenho um Forerunner 255S e há algum tempo estou tendo problema de registro do pace. Vai bem até uns 25 minutos de corrida, depois começa a oscilar drasticamente, indo de 5:20 a 9:30 em segundos e sem ao menos eu diminuir o pace. Também percebi na corrida de ontem que ele marcou erroneamente a altimetria. Já voltei para as configurações de fábrica, uso o total + multibanda. Mais alguém com esse problema?

My Forerunner 255 is failing to record my sleep.

1345609 — Mon, 07 Sep 2026 16:27:05 GMT

My 255 suddenly started having issues recording my sleep score. All my settings are correct and haven’t changed, I have the watch tight enough on my wrist so that there’s no chance of it losing contact, it’s charged and I have no activity active or pause (like running, walking, etc). It’s recording all of my other data continuously throughout the night (heart rate, body battery, HRV, breathing rate, etc) just no sleep score. I’ve been sleeping soundly and have my sleep window on my watch set the same way it’s always been (11pm-9am). It’s worked perfectly fine for the past year then suddenly does this even though no changes have been made. I double checked all my settings and they’re correct. I also looked for updates and everything is up to date.

Strava pulling through incomplete watch name from Garmin

jamiebee — Mon, 07 Sep 2026 08:57:00 GMT

Up until mid August, Strava showed my watch name as Garmin Forerunner 255 Music. For some unknown reason, since then it is showing as Garmin Forerunner 255 on all activities. I’ve tried removing the watch and adding it again on both Strava and Garmin. I’ve also tried signing out / back in again on both.

I’ve shown some screenshots from my Garmin Connect app showing on my Home page, the watch shows the shortened name but when I go to More > Garmin Devices it shows the correct name including Music at the end.

I’ve no idea why it would suddenly change for no reason. Anyone else had a similar issue and offer a solution ? It seems to be pulling through the name from where I click on the watch icon on the Home page.

wrong training detection

8102785 — Fri, 04 Sep 2026 13:06:07 GMT

for the past 10 days, my Forerunner 255 has started detecting my bodybuilding sessions (three times a week) as low aerobic instead of anaerobic. As a result, my training status changed from unproductive to unbalanced. These activities are exactly the same as before, when they were recorded as anaerobic. I have already tried wearing a chest heart rate monitor and I have already installed all the latest software updates.

Does anyone please have the 255 music 28.05 FW file?

1860424 — Thu, 03 Sep 2026 11:02:31 GMT

Wanted to have a backup before I upgrade to 29.05 🙂

Update 29.05

6544718 — Wed, 02 Sep 2026 09:48:38 GMT

I noticed some bugs since the new update was installed.

Speed in activity was not always displayed.

Training status stopped working.

Sleep status stopped working.

I am the only one?

R255S OWS distance bug – distance systematically lost after direction reversals (FIT/KML evidence)

kegnatz — Thu, 27 Aug 2026 12:31:24 GMT

I think I have found a reproducible Open Water Swim distance-processing issue on the Forerunner 255S.

This appears related to the previously reported “Forerunner 255 wrong open water readings” issue, but after several controlled tests I found a very specific and reproducible pattern:

the first straight leg can be measured correctly, but after reversing direction the OWS-calculated distance becomes systematically shorter than the distance represented by the GPS coordinates recorded by the watch itself.

Device: Forerunner 255S
Software: 28.05
GNSS: All Systems + Multi-Band
Recording: Every Second in the main tests (Smart Recording was also tested earlier)

Clearest test: 25 out-and-back legs, LAP at every turn

At a second location I swam 25 repeated approximately 60–65 m legs, pressing LAP at every reversal.

The first leg was essentially correct:

Lap 1: Garmin 63 m / GPS-coordinate geometry ~64.7 m

Immediately after the first reversal:

Lap 2: 49 m
Lap 3: 54 m
Lap 4: 55 m
Lap 5: 51 m
Lap 6: 56 m

...and the same pattern continues through the activity, with most subsequent laps around 44–56 m.

The key observation is:

START → first leg = correct
180° reversal + LAP → next leg = too short
another reversal + LAP → next leg = too short again
and the error repeats

Manual LAP therefore does not appear to reset whatever is happening in the OWS distance calculation.

Garmin Connect screenshot showing all 25 original lap distances:
https://github.com/kegnatz/garmin-fr255s-ows-bug/blob/main/Screenshot%202026-08-27%20at%2013.48.29.png

Complete FIT/KML evidence ZIP:
https://github.com/kegnatz/garmin-fr255s-ows-bug/raw/refs/heads/main/garmin_fr255s_ows_FORUM_FINAL.zip

Evidence repository:
https://github.com/kegnatz/garmin-fr255s-ows-bug

The GPS track itself is substantially longer

This does not appear to be explained simply by poor GPS reception.

When I calculate the geometric path length from the GPS coordinates recorded by the watch in the FIT/KML, the 25-leg activity is approximately 1595 m.

In other words, the watch has GPS positions representing substantially more movement than the OWS distance calculation credits.

This suggests that at least part of the missing distance occurs after the GPS positions have already been recorded, in the OWS distance-processing/filtering stage.

Test with only ONE reversal

To test this further, I did a much longer swim with only one major direction reversal, approximately halfway through, without pressing LAP at the turn.

Garmin KML GPS geometry: ~1509 m
Garmin reported OWS distance: ~1480 m

The first ~750 m leg appears to be measured normally. After the single reversal the activity ends approximately 29–30 m shorter than the geometry of Garmin's own GPS track.

Control test: one straight leg

I also recorded a simple single-leg swim with no reversal:

GPS-track geometry: ~158 m
Garmin displayed distance: ~160 m

So the same FR255S can measure a simple OWS leg essentially correctly.

Earlier tests show the same pattern

In previous repeated-leg tests I obtained approximately:

1491–1493 m Garmin GPS track → 1355 m reported OWS distance

and

~1515 m Garmin GPS track → ~1380 m reported OWS distance

Switching from Smart Recording to Every Second did not solve the problem.

I also tried wide, continuous rounded/figure-eight turns instead of stopping and making sharp 180° turns. Garmin simplified those curves in the recorded GPS track, but the calculated OWS distance was still materially shorter than the geometry of Garmin's own recorded coordinates.

My working hypothesis

My suspicion is that after a substantial direction reversal the FR255S OWS filter temporarily interprets legitimate movement in the new direction as GPS noise/drift and does not add all of that movement to distance.

After some time it appears to accept the new direction again.

That would explain why:

no previous reversal → first leg is correct

while

after reversal → the beginning of the next leg loses distance

and repeated reversals allow those deficits to accumulate.

Garmin engineering should be able to verify this directly by comparing FIT Record position_lat / position_long with accumulated distance immediately before and after each reversal.

Manual LAP clearly does not prevent the behaviour.

I would also be interested to know whether REST resets this internal state while LAP does not. I have not used a REST test as evidence here. Even if REST works, however, LAP followed by swimming in the opposite direction is a perfectly legitimate OWS use case and should not systematically lose distance.

Separate pre-start GPS issue

I have also seen another potentially related behaviour.

Before one swim I opened OWS and waited stationary for more than two minutes for GPS lock. I then entered the water, moved to the actual starting point, raised the watch above water and waited until GPS was green again, and only then pressed START.

Nevertheless, the exported activity used the earlier pre-start GPS-lock position as its starting point.

Files and methodology

Any manually drawn Google Earth route I used while investigating this was only approximate and is not being treated as ground truth.

The main evidence is the comparison between Garmin's own recorded GPS coordinates and Garmin's own calculated OWS distance.

I have also submitted this to Garmin Support.

Could anyone with a FR255/255S reproduce this?

A particularly useful test would be:

swim repeated equal-length out-and-back legs → press LAP at every 180° turn → compare Lap 1 with the subsequent laps.

I would also be very interested in the same test on other Garmin models to see whether this is specific to the FR255 OWS algorithm.forums.garmin.com/.../garmin_5F00_fr255s_5F00_ows_5F00_FORUM_5F00_FINAL.zip

Forerunner 255 Series - 29.05 - 100%

Garmin-Kevin — Wed, 26 Aug 2026 17:50:50 GMT

Software Version 29.05 is now available for Forerunner 255 Series. You may manually download this software update by following the path below:

Menu > System > Software Update > Check For Updates

Change Log

Fix an issue with syncing strength personal records to Garmin Connect.
Fix an issue with configuring heart rate and power fields from Garmin Connect Mobile.
Various bug fixes and improvements.

Looking for 255 music old firmware version

9489451 — Tue, 25 Aug 2026 17:08:48 GMT

Hello,

I've just updated my Forerunner 255 Music to firmware version 28.05. Since then, my battery has been draining super fast and the HR sensor has stopped working entirely.

Since Garmin's customer service hasn't been helpful at all (they only offered me a 20% discount), I would like to roll back my firmware.

Does anyone have the 27.09 or 22.22 firmware version for the 255 Music?

Thanks a lot!

Pokémon Sleep: I Choose You" watch face not available for Forerunner 255

2448819 — Tue, 18 Aug 2026 09:56:48 GMT

Hi,

I noticed that the "Pokémon Sleep: Snorlax & Friends" watch face is available and installable on my Forerunner 255 Music, but "Pokémon Sleep: I Choose You" (Connect IQ Store link: apps.garmin.com/apps/880e3034-3e6e-4521-88d4-a208f2406b66) does not list the Forerunner 255 as a compatible device.

This seems inconsistent, since even less powerful devices like the Forerunner 70 and Forerunner 165 are listed as compatible with "I Choose You," while the Forerunner 255 is not despite already supporting the other Pokémon Sleep watch face.

Is this an oversight, or is there a specific technical reason the Forerunner 255 isn't supported? Would it be possible to add support in a future update?

Thanks!

Calories not synced for the first time

w456w56 — Mon, 17 Aug 2026 07:54:35 GMT

On sunday 16th August the recorded edge 540 and hrm pro plus activities (only calories) not synced to the fr255 music.
On the connect app/web everything okay, but the watch didnt get the sync nor over wifi sync neither over bluetooth/connect sync.

I accidentally recorded a multi-sport as all swim. Is there a way to fix it?

DrewKime — Sun, 16 Aug 2026 14:54:21 GMT

I ran a triathlon and had multi-sport configured to long-press the lap button for transitions. During the race I forgot and just short-pressed, creating new laps but not changing activities. Is there any way to convert this to the correct activities?

I also recorded the ride on my Edge 530, so I've got all the cycling data. For the run I probably won't get cadence, but HR and pace should be there based on the GPS.

FR255 Music (28.05): RTL Trap 0x037 reboot loop — only when paired to a phone, crashes ~38s after boot

3324465 — Sat, 15 Aug 2026 18:04:14 GMT

Device: Forerunner 255 Music Software version: 28.05 (Production, current stable) Phone: iPhone, Garmin Connect iOS (current version) Started: approx. one week ago

Symptom

The watch becomes extremely sluggish and reboots on its own as soon as it is paired with a phone. Starting an activity triggers a crash and an automatic restart; the activity usually only starts successfully on the second or third attempt. Battery drain is severe during this.

What isolates the problem

With the Garmin Connect app removed from the phone, the watch runs perfectly — including starting activities. No lag, no reboots, normal battery drain.
As soon as the watch is paired again, the problem returns immediately.
I paired a second, different iPhone with a clean Garmin Connect install. Same behaviour instantly, so this is not phone-side leftover data.
The watch also crashes when connected to the charging cable, so this does not look like a voltage sag from an aged battery.

What I have already ruled out

Firmware is current: 28.05 installed and verified over USB with Garmin Express. Not on beta.
Storage: ~3 GB free.
GARMIN/NEWFILES is empty. GARMIN/ACTIVITY holds 190 files.
GARMIN/RemoteSW contained only one leftover package (006-D9033-01.zip), which I removed.
No Connect IQ apps, data fields or third-party watch faces installed.
Smart notifications disabled — no change.
Bluetooth sensors and accessories cleared.
Soft reset (LIGHT held) performed multiple times.

Crash log

ERR_LOG.BAK from the Debug folder (unit ID redacted):

json

{
  "product_name": "Forerunner 255 Music",
  "software_part_number": "006-B3990-00",
  "system_version": "28.05",
  "build_type": "Production",
  "error_cause": "RTL Trap",
  "proprietary_info": {
    "Time": "2026-8-15 12:38:40",
    "uptime": "38495",
    "pageStackDepth": "1",
    "pageStack": "1799",
    "RTL Error Number": "0x037",
    "programCounter": "0x10001835",
    "stackPointer": "0x30410768"
  }
}

Two things stand out to me:

Uptime is 38,495 ms — the watch crashed roughly 38 seconds after boot, which is the window in which it establishes the phone connection.
RTL Error Number 0x037. The same error number appears in an existing Connect IQ bug report for the Venu 3S on 17.05, filed under the title "RTL Trap with CONNECTION_STRATEGY_SECURE_PAIR_BOND" — i.e. in the secure BLE pairing/bonding path. That matches my trigger exactly.

The backtrace repeats one address nine times in a row and the block below it returns to its own entry address, which reads like recursion. Several registers are 0xffffffff. I can attach the full log including the backtrace and register dump.

I also pulled CFX.TXT and went through the page transitions: about 216 pushes against 203 pops over 128 hours, maximum page stack depth 10. Nothing pathological at UI level, and page 1799 from the crash record does not appear there at all.

Question

Is this a known issue in the BLE pairing path on 28.05, and is a fix in progress? Since the crash appears to be in firmware rather than in user data, I assume a factory reset will not help — happy to be told otherwise.

For now I am running with Bluetooth disabled and syncing over USB with Garmin Express, which works without any issues.

Happy to provide the full ERR_LOG.BAK, CFX.TXT or the complete GARMIN folder to support if that helps.

Trouble with max HR

5515057 — Sat, 15 Aug 2026 13:27:48 GMT

After max HR was set higher on two occasions automatically, all my following runs were registering as low aerobic even though they felt like proper exercise. I lowered max heart rate because it was unlikely high from 202 to 177 using the age formula (I'm 43) . Now all my runs are registering as extremely high aerobic or high anaerobic but I feel the effort is similar to before (when it was registering as low aerobic). And my Vo2 is going down (sob). Is there any way to fix this? Feels like my watch is completely useless now and all the information it gleans is skewed. I've been using it for a year. I live and run in a very hilly place, for instance today's 4 k run had a difference of elevation of 85 meter. Heard somewhere that it could affect how Max heart rate is automatically set.

HR/ cadence problems

6448941 — Fri, 14 Aug 2026 08:32:47 GMT

I’ve been dealing with this problem for quite some time now. When I start running, my heart rate is very low—almost unreal for someone who’s running—and then it suddenly shoots up to 170 or 175. This usually happens around the 1-km or 1.5-km mark. My watch is on properly, and I’m sweating normally. The watch is less than a year old.

I’ve read here that it’s a common problem called “locked cadence,” but I don’t really see the connection. Can you explain it to me?

Does anyone have a solution for this? Something other than buying a heart rate strap. The thing is, it suddenly started acting up. Is it a software update issue? Problems with a low-quality Optimal sensor?

Thanks in advance!

No altitude measurement

hogberg75 — Thu, 13 Aug 2026 21:07:18 GMT

For some reason my Garmin has stopped to measure the altitude while running or cycling. I have the latest software 28.05 and I have it on auto calibrate and I've also done it manually but after an activity it still says 0 meters. The problem started end of June and but in mid July it worked again, but since beginning of August it stopped again. Does anyone have any idea on how to fix this?

Uhr vibriert

0ff60ffd6b01411995ba90232232f921 — Thu, 13 Aug 2026 08:22:25 GMT

Hallo zusammen, seit ein paar Tagen vibriert meine Uhr ohne Angabe eines Grundes in unregelmäßigen Abständen für 1-3 Sekunden.

Hat jemand dafür eine Erklärung?

hr pro icon doesn't appear on Garmin Connect open swim work out

FabioSaitta — Fri, 07 Aug 2026 16:40:28 GMT

I have just changed battery of hr pro. I have my hr pro on my chest on land I select open swim wait for hr-pro connected then wait for GPS signal then go inside sea, swim 50m far from shor. Lift my left hand and wait for GPS green and start swimming. When I finish my workout I stop the activity, go outside sea, save the work out. 255 looks for hr pro, download data, save then upload the work out usually without yellow icon for HR-pro strap forums.garmin.com/.../hr_5F00_pro_5F00_open_5F00_swim.zip here there is the fit file with both wrist and chest HR. Are there anyone who swims with hr-pro and have the save issue ?

Restarts when wifi syncing when low on battery

7714909 — Sat, 01 Aug 2026 23:55:15 GMT

This has happened twice.

I use wifi to sync. Bluetooth is not on, unless sync refuses to work.

Twice recently the watch has restarted when it is low on battery.

The main issue is I lose stress data since last sync before this in the app, even though it’s still in the watch.

Bluetooth sync does work at that stage.

This watch is a few years old. I believe Januar 2024. 255s Music.

Why does this happen? Should I restart the watch now and then? I always restart after a software update.

ALERTAS

Juan-Elmalu — Fri, 31 Jul 2026 10:45:52 GMT

Hola, Tengo un entrenamiento de carrera creado con Garmin Connect para 10 KM, con objetivo por ritmo entre 5:00 y 5:30 min/km, y en las alertas de la actividad de carrera he activado la alerta por zona de FC, pero no me saltan, en el modelo 165 de un amigo si que le funcionan, esto es lo normal o es que hay que activar algo mas.

Gracias

Notifications: Forerunner 255 not receiving phone notifications

8368951 — Tue, 28 Jul 2026 07:49:55 GMT

The last month at least, if not longer, my Forerunner has not been receiving notifications from my phone. No messages, no phone calls, no application notifications.

I've read every tutorial and guide on turning on notifications. I never turned them off, I've had this exact setup (watch+phone) for over a year without issue.

All notification settings are on (including all apps), in the Garmin watch, in the Garmin connect app, and my Samsung notification settings. Battery optimisation is turned off for the Garmin connect app. Battery saver is turned off on both devices. Do not disturb is turned off on both devices. Garmin watch updates are set to automatic, but my mobile updates are manual and I have not updated my version of android. Put plainly, I have changed nothing and all of a sudden the functionality is gone

I've noticed that if I turn the settings on and off in my connect app, I might get a few notifications, before they just turn off for good.

I can't seemed to find anyone else dealing with this at the moment. Any help is appreciated.

Forerunner 255 stops showing heart rate and discharges very quickly (from 100 to 10 within hours) after the update

1299652 — Mon, 20 Jul 2026 09:45:57 GMT

Yesterday i updated my Forerunner 255 to the last version (28.05). After that it started discharging very quickly and then the green lights of heart rate monitor stopped. And the heart rate isn't displayed on the watches. I did reset - this didn't work. Connected to my PC with Garmin Express software - also no result. The Garmin PC shows that all the updates are installed successfully but the heart rate monitoring function doesn't work

Garmin Coach: Final recovery interval skipped before Cool Down

Arno — Sat, 18 Jul 2026 18:05:44 GMT

During Garmin Coach interval workouts, the software systematically skips the final recovery step after the last fast interval. The watch immediately switches to Cool Down. This is physically frustrating, as a recovery phase is highly needed right after the final hard effort before entering the actual cool-down pace. Please fix this logic in the workout loop so that the last recovery step is executed properly.

Thank you in advance,

Arno

BUG: Activity Clock Data Screens UI Issue

2856561 — Thu, 16 Jul 2026 00:55:19 GMT

Hello,

I got my hands on a Garmin Forerunner 255 Music 46mm.

I started an indoor walk activity (should be similar to any other activity) and navigated to the clock data screen.

When I have too many "icons" active (battery, phone connected, alarm active, headphone paired), they seem to be cut off at the edges (see below). If one of the icons is removed, it looks fine.