D2 Delta battery draing and heart rate monitor sporadic

Hi

Happened overnight and with no warning signs: the battery of my D2 Delta started to drain within half a day (need to be charged every night whilst had to charge every 3-4 days). At the same time, the wrist heart rate leds are not flashing anymore as usual and they seem to pickup the heart rate only during exercising and somewhere above 100 bpm and never below.

I tried a hard reset, a factory reset, a system update and even switching off the heart rate monitor. The battery is still draining.

Both things happened on the same day so. I tend to believe they are linked.

Any clue?