With the current SW version, 6.1, even worse than out of activity HR, is the broadcast HR mode. While indoor bike training I broadcast my HR using the F6X and the results were way to low, ie while climbing it was showing my HR at between 60-70 bpm. I switched to activity mode and the HR immediately corrected itself and jumped to between 110 - 120 bpm. This was repeated on two separate days with very similar results. I than tried to exit the activity and did notice that outside of activity was somewhere near the 110 bpm which is far more believable than the broadcast mode of 60 or so bpm. Garmin, this is easily duplicated on my watch and doesn't seem to be sensor issue but rather a bug in the broadcast mode. Please look into it.
