It happened during a marathon on September when suddenly the hr jumped to 180 bpm from 140... During the the last 3 running session, was really unrelaible showing a too high frequency instead of my normal hr during the same kind of training sessions, usually 130/140 bpm. I'm really disappointed about this, my old 935 worked perfectly.
Please help me to fix this problem, I've already did the factory reset, but nothing has changed...
