Heart Rate Bug, Rapid rise

yes, having the same problem

Yes, same issue here!

Please put me on the list as well, thans

Hello - I am having the same issue as well, primarily on higher-effort runs but also on low-effort or strength training exercises. Attached is an example from my run from yesterday (5k race), where my heart rate suddenly jumped by 25 bpm to ~195. Nothing changed in the race at that point and I did not feel noticeably different, so I am certain this was a bug. I've had this happen on most of my races and have the watch as tight as I can (which did help a little, but not completely).

Agreed with the other posters - for a higher-end watch I would not expect this to be an issue. I never had the same issue with my older FR245M; only since I got the FR965.

Exactly the same here!

For me this looks like a bigger problem regarding the HR, not even related to running and not new.
A few months ago i contacted the support because i had the observation with my fenix 6 pro that the HR measurements were completely wrong when i am walking around or on a hike. I.E. when the watch shows a hr of 100 i often have 70 in reality.
Support was asking how i checked this and seemed to be waiting for my answer as a trigger for a standard answer: i answered that i compared to a professional heart rate monitor. Support told me that i shall not do that, because the garmin HR-monitoring is not a medical monitoring device... okay, after a short discussion, support told me that i should throw away my watch when i am not satisfied.

One of the big problems i see: because even normal walks are often registered with wrong heart rates (and outside of trainings it is not possible to correct this by wearing a belt) every calculation of the watch is wrong, i.e. calories, training load over the day, recovery...

Now i got a FR965. Here is a recording of a leisure walk in the park. Wrist HR and step rate. It looks as if the watch is trying to lock the HR to the step rate. At around minute 40 i recognized that the HR is wrong. I checked by counting with a stop watch and got 60 instead of the shown 100.

Then i decided to simply turn the watch from outside to the inside of the wrist - and immediately measurement was okay, values changed from around 100 to 60. Well, wearing inside i am not able to see the display, so this is not really a solution.

I have one easy run with such a sudden and unrealistic HR spike too. In my case it was at the beginning and the HR rose to 180 very quickly. I took out the watch and secured it again which apparently helped.