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

Yep - the pace average (started with v17 i think) is very annoying and makes it near impossible to run a set pace now as the averaging is over such a long period.
Previously it was a few seconds, now its nearer 20.

I got the updated firmware as soon as it was released.
As a mid distance runner I ran two races (Cross country 10k championship, 5k road race). For those races the heart rate recorded, was in average quite lower with other races I have ran this year, but for me it was max effort. 
Then I have also completed some interval training (400 repeats, 1000m repeats)...total chaos there.
In some easy runs the sensor works better but still there are obvious issues.

18.22/18.23间歇训练（400 次重复、1000m 重复）......完全混乱。

Here is an update from my side: I ran a steady 6:45 on a straight run yesterday and then increased my pace to 4:15 and held it for 1 minute. My heart rate, which was definitely around 175, was almost completely ignored by the watch. Only at the end of the minute, when I went back to walking pace, did the watch realize that something had changed.

I'm so mad that that this thing even made me shave off my few arm hairs to rule out this error too. Garmin support, which I have also contacted in the meantime, says there is no problem and that I should wear the watch properly.

A new day, a new suggested workout from Garmin. 40 min "Basic" run at 7:00. I'm running along and as I'm totally untrained at the moment, I think the heart rate of 130bpm can't be right, it feels higher. So I stop to measure the correct value manually and suddenly the watch also realizes that my heart rate is actually over 150bpm. At this point, I really have to say that the heart rate measurement of a cheap MiBand works better. 

Hi, thanks for the reply and for pointing out once again that since the update it seems I simply have no idea how to wear a smartwatch correctly.

If the poor OHR results are due to the fact that I'm wearing the watch incorrectly, I'd like to understand why it worked perfectly a few software versions ago?

Or why I should suddenly switch arms if it worked perfectly on the left arm a few software versions ago?

I have already contacted Garmin support and they told me that there is no such problem and that I should wear the watch correctly.

I'm just at my wit's end, as I haven't changed anything apart from the update and the shaved hair around the watch. I have no tattoos and as you can see, I wear the watch above the ankle and it is just tight enough so that it is not too tight but not too loose either. When I move the watch slightly, my skin moves with it.

It is what it is: Garmin has rendered my watch completely unreliable for me with the update.

6742038

I am sorry it sounded like I assume everyone is wearing their device incorrectly. That is not the case. I wanted to point out that it is important how you wear the watch, among the other tips I listed. To some users, those tips are already part of their routine and they are still seeing inaccuracies. That's why I asked for users to reach out to support, so our agents can view everyone's examples of those inaccuracies and get them reported. We are looking into a report of all of these examples and are in the middle of reviewing them and seeing if we can approve. I see in your chat with Support that we did not get any examples, and we need those to add you to the investigation. I will send you a message to make sure you're added to our investigation, but request that everyone else reaches out to get those examples to us!

Hello, yes, that's how it sounded to me. But English is not my first language and I misunderstood, sorry for that. Anyway, I don't want to be part of an investigation team and I don't want to give permission for my connect account to be reviewed.

I basically can't prove anything I'm claiming because I don't have a heart rate chest strap yet. So even if I find out for myself that the OHR completely ignores my heart rate spikes during interval training or is way off at times, I can't prove the true value at that time. Somehow I find "trust me bro" a strange source here. I mean, heart rate is a core function of the watch on which so much of the evaluation data depends.

After clicking through the previous beta program bug reports and the forum in general, I realized anyway that it was pure coincidence that the OHR has worked so well for me so far. And since this is a recurring theme throughout all versions, I have now decided to buy a heart rate belt to at least put this particular problem behind me.

I mean, after so many software versions, the watch still randomly crashes and restarts itself. But that belongs elsewhere.

This is my HR graph, swimming yesterday - suddenly not naturally changed in the middle of the activity (no, I am not a swimming robot ;-) ) My HR graph