HRV Algorithm change after latest update?

So such ongoing changes for me:

Any chance you're fjghting an infection?

Mine is tracking as normal since the upgrade 

Thanks for replying. My hayfever has kicked in, but I get that each year. I've not really tracked my HRV that much, but it does say that having bad Hayfever can cause HRV to drop while the body fights itself for no reason

I think this is a problem, I have had these changes for several months even before the update to 21.19. And as the system updated to 21.19, this became constant every night, the pulse rate drops to 20 beats per minute. This is unrealistic. Then after a few hours it increases to real values. (Fenix 7 Pro Solar)

ltdfoto.ru/.../sfoZfo

and so every night there is a drawdown

dips absolutely everywhere: swimming, walking - constant dips, during sleep - dips, even sitting in the office at work and watching how the pulse drops to 50-55, then sharply increases to a real 75. The heart rate monitor lives its own life. unstable operation of the heart rate monitor affects hrv dates. The most annoying thing is that the official dealer after checking said that everything is fine. But I know how it was half a year ago, when everything was working properly. I thought that the new version 21.19 solved this problem, but it seems to have gotten worse

I don't think this is related to HRV algorithm itself but to the OHR going havoc when HR is changing rapidly. If HR is stable - like during the night I can't observe differences > 1 or 2 ms between my everyday system on 15.77 and my test unit on 21.19. 

I'm doing a little comparison testing with simultaneously wearing a unit on 15.77 and one on 21.19. I described the scenario I use in more detail here:

https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-7-series/413518/altimeter-barometer-not-accurate-anymore

As for the OHR disaster more here:

forums.garmin.com/.../wrist-heart-rate-still-broken