Battery drain after factory reset

Bangle._PWR is undefined for me. Do I have to enable it somehow?
And I tried leaving the watch disconnected from everything—didn't change anything.
Also, I seem to have misremembered when exactly the battery problem started; I checked the battery log (relevant part is attached as a screenshot), and it seems that

1. I was charging the watch the day the issues started
   
2. After I disconnected the watch from the charger and until it froze, the battery was also rapidly discharging
   
3. After I rebooted the watch the discharge rate was normal, and, even after the factory reset, it was normal for more than a day; only the night between 22.10 and 23.10 it started rapidly discharging—seemingly randomly.
   

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