Forerunner 945 strange situation with measuring my heart rate during a running workout

Hi all.
I decided to raise the topic and ask a question. Is there a way to downgrade the firmware? I currently have 13. On my computer there are folders like PrimaryFirmware_PrimaryFirmware.006-B3113-00.12.51 with GUPDATE.GCD files. If this is an old firmware version, how can I install it? If not, where can I get previous versions?
Support refused to help me under a false pretext. I appeal to the community.

Thank you.

thanks for the answer. yes, as far as I know, I have tried all the ways of overloading. As an engineer, I can assume a software problem precisely because the problem does not repeat itself every time, but quite often. It correctly calculates your pulse at night and during normal use without activity. When I run I don't see any breathing measurements, I don't use anything other than my watch. the night dimension is present. the number of failures is about 8 out of 10. I haven’t checked the trailrun yet, thanks for the advice. After the failure with my HRM-pro problems with the clock make me sad. This is unacceptable for such expensive devices.

Do you have tattoos where the watch is placed on your arm?

You can try to switch arms or put the watch on the back of your wrist and see if there are any differences.

thank you for message. no, there is no tattoo on my wrist. I tried hair removal to fix this problem. I also tried trail running and tried changing activities. I even tried just running, without including classes. and here's what I noticed: the problem occurs even without the mode running. in my opinion, this is always when the pulse crosses a certain limit within a few minutes. As an engineer, I can assume that the situation may be related to some buffer overflow when the device cannot cope with data processing. This may sound strange, but at the moment I don’t have any reasonable guesses. After all, after a while, the pulse count returns as if nothing had happened.
I will check your proposal, although it is inconvenient for me, thank you.

I checked it on your other hand according to your advice. as expected it didn't work. So I ask you again to tell me how I can roll back the firmware from the current version 13.

I don't know of any method to downgrade the software.

I checked my activities for the same error but I almost always use a chest strap, but sometimes I forget to put it on. The logged heart rate is working every time.

Have you done a factory reset?

Yes, sure. and more than once. It was because of this that I asked for help in downgrading the firmware.

Hi Sergey,

I have exactly the same problem as you. In addition, the problem also exists general and not only during an activity. My stress evaluation is also affected. Here too, there are always no values.

I would also be interested to know if it is possible to downgrade the firmware.