Heart rate sensor issues

Hi everyone, I'm bringing up a topic I posted on the Garmin Beta forum. I now have version 26.08 stable and this problem still occurs. I posted a similar problem on the beta forum, link:

 Unusual heart rate deviations during activity 

Other users have a similar problem, link:

 Heart rate 

Please let me know how it looks on your end. And I ask Garmin to look into this, because the FR 965 was, after all, a top running watch not so long ago. I know they read the posts and comment :) Thank you and best regards, Tomasz

I found the solution for perfect wrist readings, and with this solution,
my 965 is extremely accurate!!!
You have to wear the watch upside down, with the sensor resting on your veins, and quite tightly on the inside of your wrist!
I can guarantee it doesn't miss a beat, even at rest or at night!
It may seem uncomfortable at first, but I quickly got used to it, and it records perfectly!

I had another bad HR reading during my run. Again the same happened:

1. Put on my Polar H10 chest strap

2. This time I even entered the watch's system menu and Sensors & Accessories and checked that it connected to the strap (via ANT)

3. ran

4. during the ran I realized that my displayed HR suddenly dropped, even though I was pushing harder and could breath harder than a minute ago

After I finished the activity I again uploaded it to fitfileviewer.com and looked at the graphs. I was shocked to discover that for the WHOLE activity I was displayed (and recorded) the wrist HR, and for exactly 0 seconds the HR from the strap.

How do I know? I also have my datafield installed, that records the HR from the strap directly via ANT (even if (actually only if) it's not connected to the watch in the system menu) This is it if someone wants to try: https://apps.garmin.com/apps/7c83d402-4b68-4f0a-b167-7139788a19b3 Here's how the comparsion looks like:

[can't upload image...]

The "heart rate" has a 100% match with "wrist heart rate" and as you can see on the image it has virtually 0 match with the ANT HR.

After I saw this I disabled "source switching" in the watch, though it looks as this won't help a lot, because it's not that the watch decided to switch over to the optical sensor in the middle. It was only recording from the optical sensor since the beginning.

What's disturbing even more, is that since the HR measured by the watch was 15-25 bpm lower that the actual, all the other measurements are screwed. In particular at the end of the run my lactate threshold and max HR were both automatically changed. My run was deemed to be a base run.

Garmin-Eiliko  FYI. fr965, FW: 26.08