Brand new Fenix 8 purchased ︎ Updated to 13.35 18 hours later: it cannot measure (nor record) HR and any other HR activities

[UPDATE: FIXED] I went back to the Garmin shop:

1. They reset the watch, the issue was still happening.

2. They then updated the same firmware from the Garmin express windows app, the issue was still happening.

3. They deleted all activities and then factory reset the watch, the HR started working again but with 20 bpm lower difference in comparison with another Fenix 8 they had on display.

4. We waited 10 minutes and the numbers started to equalize.

[UPDATE: The FENIX 8: 43mm AMOLED (fw: 13.35) has its HR monitor broken again!]

Seriously, I do not wish anyone to experience this. Hence why I take the time to document this.

GARMIN 13.35 Update BUG - HR monitor stops working under some situations and starts working after some luck but not always!

Steps to reproduce. Here the log of every actions I've done. I hope this helps the QA to identify the issue and the developers to fix it:

```
// ️ At this stage the HR monitor has stopped working again
- I select "Delete Data and Reset Settings" [Hard reset]
- I deleted the Glances Health containing the HR
- I disable the HR sensor by setting Status: off
- I perform a soft reboot by holding the light button for 15 seconds
- I enable the HR sensor again
//  I see the HR on my watch again!

Now let's try to reproduce the bug again:
- I've deleted the watch from my Garmin Connect app & removed its connection from the bluetooth.
- I connect the watch on my phone by adding device
- I set the watch in pairing mode by going to Connectivity
- Connection is successful, I'm on the: "Almost done! Sync your device." screen on the app
// I still see the HR on my watch
- "You're all set" screen
- skipping onboarding screen on how to use the watch
- skipping "Set up wi-fi" screen and tap finish.
- tapping NOT NOW on "congratulations on your new fenix 8 - 43mm, AMOLED" dialog screen with [GET STARTED] [NOT NOW]
- syncing the watch
// I still see the HR on my watch

// This is where I start filming with my phone. Here the video:
// https://youtu.be/d4DzHwUvpzw

- Connecting the watch to the Mac via USB
- disconnecting the watch from Mac
// I still see the HR on my watch

- Connecting the watch to the Mac via USB
- Starting Garmin Express (v7.24.0.0 (695f9f43e))
- Clicking on the watch on the Garmin Express mac app
- I click on sync
- Sync is successful, not update required
- I put the watch on my wrist again
// ️ I don't see the HR monitor number on my watch

- I disable the HR sensor by setting HR Status: off
- I hold the light button until screen turns off itself
- I press the light button again, I see the blue triangle
- On reboot, the HR reappears
//  I see the HR on my watch again!

- On the mobile app, I'm editing Glances while being on the HR broadcasting screen in order to monitor if the HR sensor stops working while I customise the Glances to my preferences
- I create a Health folder with: Body battery, Calories, Health Snapshot, Heart Rate, HRV Status, Pulse OX, steps, I save it
// I still see the HR on my watch

// I start walking and 5 minutes later I don't see the HR monitor anymore
- So I delete the glance Health folder I've created
- I perform a soft reboot by holding the light button for 15 seconds
// I don't see the HR monitor number on my watch
- I disable the HR sensor by setting HR Status: off
- reset default settings [Factory reset]
- delete device on Garmin connect
- add device, repair watch with Bluetooth
- go through onboarding
- the default health folder shows DISABLED (for some reason the reset default settings still remembers that I turned off HR status , is that actually normal?)
- I delete the Health (default) Glance
- I add Heart Rate glance which says Disabled
- I enable HR status
- HR monitor still displays "--" instead of a number
- I power off the watch normally through the carousel while leaving my Bluetooth ON on my android phone
- I turn the watch on
//  I still don't see the HR monitor number on my watch
- I turn off Bluetooth on my phone
- I reboot the watch normally via carousel
//  HR starts working again!!

// I stopped looking at the watch for 20min.

- I look at the watch 20min later
// ️ I don't see the HR monitor number on my watch anymore
- I check my phone bluetooth and it is still OFF, so no sync had happened yet.
- I switch off HR status
//  I still don't see the HR monitor number on my watch
- I reboot normally the watch
//  I still don't see the HR monitor number on my watch
- I delete all activities
- I enable HR status, HR monitor still displays "--" instead of a number
- I disable the HR sensor by setting HR Status: off
- I power off the watch normally through the carousel
- I turn the watch on after waiting for 1 minute
- I enable HR status
//  I still don't see the HR monitor number on my watch
- HR monitor still displays "--" instead of a number

- I select "Delete Data and Reset Settings" [Hard reset]
- The watch reboots, my phone bluetooth is still off.
- After loading the maps, it asks me to pair with my phone.
- I select to NOT  "pair phone to enable connected features",  no passcode, default text size, Metric units, 24H, M-D-Y, Male, enter my Birthday, my weight, my height, Left wrist, bed time, wake time, skip time,  for activities, navigate to Glances, I see the default 2 previews within the default Health Glance folder showing body balance "--" and Sleep "No data".
- I enter the Health glance folder
- I scroll down to Heart Rate
//  I still don't see the HR monitor number on my watch
- HR monitor still displays "--" instead of a number
- I tap on it, I see 86, then 82, then 72 and then -- again.
//  I still don't see the HR monitor number
- I delete the default Health Glance folder, without putting it back to the default glance.
- I add "Heart Rate" to the Glance
- I add to Iron Fit watch face the Heart Rate monitor to one of the allowed places where I can set it up
//  I still don't see the HR monitor number
- I power off the watch normally through the carousel while leaving my Bluetooth OFF on my android phone
- I turn the watch on
//  I still don't see the HR monitor number

// So I am going to try what worked at the beginning of this log when I managed to fix it first.
- I disable the HR sensor by setting Status: off
- I perform a soft reboot by holding the light button for 15 seconds
- I turn the watch on after waiting 1 minute
- I enable the HR sensor again
//  I still don't see the HR monitor number
- I power off the watch normally through the carousel while leaving my Bluetooth OFF on my android phone
- I turn the watch on
// ️ I still don't see the HR monitor number
```

> Note: New Garmin user like me should not experience this, especially not with a product at this price point. This is a terrible user experience. I had a Suunto Peak 9 pro before and I've never had any issue until I lost it while surfing. I wanted a watch I would never have to take off and use while scuba diving, so after a year, I got myself the Fenix 8 as a replacement. And this is my story! My first experience with Garmin ecosystem. I love the UX but I hate this bug! Without HR, I cannot monitor my Zone 2 when doing slow runs, nor my sleep quality; which makes this watch useless for me on a daily basis. And if it wasn't for the HR, well, I would just use my phone to track my runs.

If you share this experience with Garmin support, they will probably suggest that you return the watch for a warranty replacement.  You can copy and paste your description into the chat window with Garmin support.  They might ask you to upload a short video.  

With this watch it is REALLY difficult to determine if issues are due to faulty hardware or a software issue.  If you don't see everyone else clamoring about a similar software issue, then there is a good chance that it is a hardware issue.  Given that your issues didn't start until you updated software, you could try rolling back to a previous software release and see if that fixes the issue.  If you decide to roll back software and need help with the process I can post a link. 

Probably the best option is to open a chat with Garmin support and see what they say.  Chances are they will suggest you send the watch back for a warranty return.

Thank you, I would be interested in the link to downgrade regardless.

I bought this watch 5 days ago. Sending it for warranty replacement right after the purchase isn't ideal. Especially that I'm traveling and I don't have an address where they can send it back to.

I'm going back for the 3rd time to the shop I bought it from tomorrow morning, I hope I can exchange it and they deal with the replacement.

Currently the sensor "works again" as I type. And I've done nothing but leave the watch sit on the desk and put it back on again. The issue now is I don't trust the sensor anymore. I had 2 good days with it after the shop I bought it from managed to temporarily "fix" it. During these days, when I was looking at the green light sensor on the back of the watch, it was flicking like a green tromboscope every time I was looking at it. But since the issue re-appeared, the green light seem to be static and dimming itself after a second.

Now the watch turned into sleep mode itself and I'm sitting at the computer and my HR shows 80 and then drops to 35 bpm within 10 seconds and that is when Sleep mode is ON. So I turn sleep mode OFF, and now it goes back up to 60 and then stays around 53-56. I just manually took my pulse and counted for a minute my pulse and I am indeed at 56bpm; definitely not at 35.

I don't know if it's the sensor or if its the CPU that gets overloaded. No idea how they manage their operating system in there.

Thank you again for your reply. I really appreciate it. I hope this is just an isolated issue and that if I get a replacement, I won't experience this ever again. 

I don't know if this is useful but you could try going in to watch settings->system->About and then pressing the top left button rapidly around 5 times. You should then get a dev menu and the bottom option is to re-install the firmware. This might give it a kick, otherwise hopefully the next firmware will sort things otherwise it's likely some odd hardware issue and you got unlucky.

Good idea to return to the shop and let them deal with it.  Hopefully they can replace your watch with one that works properly.  

In the event that you need the instructions to roll back software, I'll provide them here.  Unfortunately Garmin doesn't provide links to every version of software, so the latest stable version of software you can revert to is 12.35.  For many people that was the most stable version.  

To go back to 12.35 click on the link following this paragraph and scroll down to the bottom of the page.  There you will find the link to download the files needed to roll back to software version 12.35.  Garmin provides this capability to roll back software in the event that Beta software causes issues with your watch.  Garmin's instruction are to: "Select the link specific to your watch model. Please note that your computer will download a .zip file when you open this link. This zip contains the files you need to backdate software, as well as a "Read Me" text file with further instructions on how to backdate."  

Here's the link: https://forums.garmin.com/beta-program/fenix-8-series/f/announcements/398518/beta-version-13-12---check-for-updates-only

Yes, the link deals with software version 13.12, but at the bottom of the page it contains the links to roll back to 12.35.  (Garmin could make this more user friendly, but I think they really want to reserve the capability for their beta testers.)

Good luck with the shop.

Replacement update:
I went to the shop, the watch HR was working again so it was almost impossible to convince them to replace the watch. They sent it to the Garmin service center. They couldn't replicate my issue; however because I've documented it and had videos of the watch failing, they agreed on replacing it  I'm very grateful for yesterday's version of me for taking all this time to document my technical issue because it helped me today and I finally have a watch with a HR mon

The replacement watch is under the previous firmware 10.23* and trust me when I'm saying this: I am not going to update this watch. Not until I see in the bug fixes log mentioning HR monitor.

About the link you provided to downgrade:
I visited the link you shared; unfortunately there isn't any clickable link at the bottom of the page. When looking at the source code of the page, I did find one .zip URL but that only was referring to the fenix 8 47mm Solar version of the watch.

Can you double check? I would be interested maybe to upgrade from 10.23 to 12.25 if you tell me 12.25 is proven safe, I disabled automatic updates for now as I'm sure it will ask me to update to 13.25 again; and I don't want to fall for this one again.

A note for the developers:
If what I experienced here was a firmware issue on 13.25, and not hardware, I believe that this issue would be due to CPU overload or out of memory issue. The reason is because last night I did nothing after hard reset the watch 5 times and the HR came back to life after 1 hour of sitting on the desk, doing nothing and I guess with the HR having a "break".

The watch on 13.25 might be doing too much at the same time. I wish I had a way to monitor FPS, CPU load, Memory on the watch itself when I did all my testing yesterday.

But here is the big thought: the Heart Rate glance feature on firmware 10.23 looks different (it has 5 coloured zones) than I remember it on 13.25 (I think it has a graph?). So this improvement could be causing the watch using too much CPU or using too much RAM.

And since all I cared about was testing the HR, I had it at the top of my glances, and I also had it in a Health folder with the HR glance at the top of the Health folder, making it displaying the HR value inside the folder in some use case scenarios.

Having a Glance folder with the Heart Rate glance at the top of the Health Glance folder might have been causing this issue and when the watch is being requested to "sync" between Garmin Express (mac version) while being connected to an Android phone via bluetooth; well... maybe the watch CPU is getting some stress there and because the HR monitor feature is a real time feature involving a calculation on the last 60 seconds, the HR is sets to fail; until the watch clears some memory.

It still doesn't explain why the HR was failing after one or 4 hard resets, but hey! I've done enough trying to help Garmin here! I'd love to have access to the source code though and debug this whole thing. That would have been awesome and fun!

bye for now, thank you!

Thank you for this tip! I wasn't aware of this! That is so cool to know the developers have added this hidden feature! I wish they would allow us to do more with it; like you can on an Android phone.

Unfortunately it looks like Garmin has removed the links from that page to enable rolling back to 12.35.  I'd be curious to know the rationale for that. I suspect it is is because the roll back wasn't entirely clean and left remnants of the 13.XX software that continued to cause issues.  

My (previous) Fenix 8 didn't have any issues until 13.31, when it started randomly crashing, at least once in each 12 hour period.  After many days of troubleshooting I rolled back to version 12.35, which seemed more stable for the first couple of days, but then the watch started crashing again.  At that point I contacted Garmin support who advised me to send the watch in for a warranty replacement.  My new watch arrived today and is on software version 11.90.  One of the first things I did was turn of auto updates.  I plan to operate the watch with 11.90 for a couple of weeks to verify there are no hardware issues, then maybe let it update to version 13.38.

Like you, I suspected the issues with 13.XX were due to some sort of memory issue.  CIQ 8 (implemented with 13.XX) introduced a new memory paging scheme.  The issues I observed on my watch were very similar to what happens on a computer with a memory leak, so I wondered if the two were related. 

I also suspect based on anecdotal evidence that Garmin introduce new power management software in 13.XX to try to address some of the complaints with battery life.  I believe the processor in the Fenix series has the ability to run at different frequencies/voltages.  If Garmin pushed the frequency/voltage too low in an attempt to conserve battery power, that could have also caused the types of issues I was seeing with 13.XX.  All of this of course is just speculation, since Garmin hasn't shared those details.  I suspect they are gathering lots of data from users that are reporting issues with 13.XX and they will continue to refine the software.  In the meantime it has been very frustrating having to rely on a watch that could crash at any moment.

Wearing my old, but still functional Fenix 5 for a week while I was waiting for my replacement watch reminded me of how nice it was to have a watch that functioned properly without any issues.  Let's hope Garmin can get there with the Fenix 8 series!

I have a very similar feeling about the issues on 13.XX and the origins about the issues.

I'm happy with the watch on 10.23 right now, it actually feels more responsive than it was on 13.35. However, I'm missing the MAIN feature why I bought the Fenix 8 over the Forerunner 965: the Garmin Dive feature. I do scuba diving and free diving quite often. On fw 10.23, the Fenix 8 doesn't support Scuba diving activities.

So I'm afraid I'm going to have to upgrade the firmware regardless; but I really don't want to experience the issues I had on 13.35 with this new watch. Especially if I'm not able to revert back. Ideally Garmin let's us choose which firmware works best.

Let me know how the watch works on 11.90 and could you let me know if the scuba dive activity is selectable on that firmware version?

If you don't have any issue with 11.90 I might ask Garmin support to send me the firmware download link to upgrade my Fenix 8