I had a long run on Sunday and for some reason I decided to use the Polar H10 strap instead of the FR 945 optical HR, even though the intensity of the run wouldn’t require a strap.
I knew at that moment that my H10 isn’t updated to the lastest FW version, but I ignored that successfully till that day – didn’t care that much.
The result was a bizarre drop of HR for a period of time during the run, I don’t know what caused it .. the sweat, the strap sensors, the H10 firmware.
Looking at the latest firmware changelog (here), I couldn’t see something relevant for the behavior I saw .. but I updated and I’ll see how things will go on from now – otherwise, it will go to support and repair.
Anyway, if you want to eliminate a potential source of issues, please update the firmware – otherwise you’ll feel puzzled like me on Sunday.