Have you also found the OHR completely useless with 18.26/18.22?

As all the others, I have found the 255 Heart Rate accuracy to be terrible in comparison to my FR245. This is on firmware 17.?? and 18.22/23. Continuously fails to track heart rate during indoor cycling (compared to arm optical HRM and chest strap HRM). Most times it takes ages to go from resting HR to zone 2-3, then eventually gets there but often drops to half or one third of this. Fails to track peak HR in race efforts, and usually drops to much lower than the HR that I know from experience and my other HRMs is correct. I'm very experienced with getting a good signal from my 245 (watch placement, band tightness). I've fair skin and non-hairy arms. The signal sometimes gets a bit better if I rotate the watch to the inside of my wrist, but not always. HR maybe a little bit more reliable when running, but it seems incredible with all their experience that Garmin can't get this fundamental thing right. Thinking of going back to my 245, very disappointed with the 255.

18.21 was the 1st time all winter i've had decent heart rate measurements. 18.22 and 18.23 were also great. Weather was cold today HR was all over the place. It's still running 18.23. There was also another update last week after 18.23 but the version number didn't change. Could just be a one off and unlikely to have too much cold weather again for months but i'm keeping an eye on this.

Hey guys, it's me again, this time with proof.

tl;dr: The OHR is working even worse than I thought. (current software version: 18.26)

I've now tested my newly purchased Garmin HRM-Dual a few times and can tell you that on the chest-strap side of life, the grass doesn't really grow any greener. Yes, my readings seem to be correct again, but the thing is really uncomfortable. You also have to let it soak up water to get any readings right from the start. Anyway, what's really strange is that apart from a brief notification that the belt is connected, there is no indication of whether it is actually sending the pulse to the watch or not, as the watch's OHR remains on at any time. There is no icon in the watch display, nothing.

I have read that this has to do with functions that Garmin wants to introduce. The public beta version 19.09 change log says: "Adds heart rate dynamic source switching to select the best heart rate data source (watch or chest HRM) to improve accuracy during running activities."

The fact that both sensors record gave me the opportunity to compare the OHR and the chest-strap data. I downloaded the *.fit file from Garmin Connect Website, read out the raw data with Golden Cheetha and processed it in Excel.

The graph shows my sprint training today: 15 minutes warm-up, 7x 20 seconds sprint with 3 minute walking and finally 20 minutes cool-down. In my opinion, it's a bad joke what the OHR has recorded. Somehow it "follows" the correct heart rate, but not really. At minute 24, it looks as if it has picked up the correct heart rate, but still completely ignores the 4 x 20 second sprints in zone 5 afterwards. All in all, the tracking would be completely worthless again today without the chest strap.

What does "select the best heart rate data source" mean for the future of chest-strap users? Will the watch then decide that my sprint training today was a low effort basic run with a maximum heart rate of arround 145 bpm because the pulse peaks seem suspicious? Will the incorrect and way to low heart rate be inserted when the chest-strap would have slipped during sprinting? With the best will in the world, I can't understand why another source of error is being slapped on top of this whole mess.

It's starting to "annoy" me that a manufacturer like Garmin can make its devices practically useless with a bad software update and still pretend there's no problem.

Finally, I would like to emphasize that I don't want to equate a chest-strap with an OHR, but there was a time when my expensive Forerunner recognized that I was doing an anaerobic sprint training and not a basic-run.

I too have had my OHR data become quite terrible. This appeared to have begun in the last couple months and I've only sorted out that it's not my health that is changing but the watch. I noticed my HRV drop continuously for weeks and became a bit concerned. Recently, while standing at my child's soccer game, I'm noticing my OHR was reading in the low 50s high 40s. My resting HR only reached this level after long consistent training, right now it's somewhere in the high 50s low 60s. I then manually measured my HR and it was in the low 80s. In the past, I've found the OHR to be quite reliable, but now to have difficulty while I'm standing still is ridiculous. I noticed in some of the previous patch notes, some changes were made to make OHR readings better in cold weather and wonder if this is the source of the problem. It's unfortunate because it has caused the majority of my health data to just be plain wrong including body battery, stress, HRV, etc. I'm hoping for a fix soon, but wanted to share.