I did turbo trainer workout. I wore a HRM-Dual strap connected to Edge 840 and recorded this workout exclusively by Edge 840. And during this workout I wore FR955 on my left wrist, but I did not use it to record workout. While Edge 840 + HRM-Dual reported ~150 bpm which is the expected value, FR955 reported ~70 bpm which is totally wrong. Also, during this workout, I noticed that FR955 shows correct HR if I shorty enable HR Broadcast or if I temporarily start any activity on it or if my HR is actually low. Otherwise FR955 shows incorrect HR.
FR955 FW version - 15.19