Battery of Boox Max 2 seem having problem

After full charged, I just make little manipulation, it decrease ~ 20%. (100 -> 80%)
After a night, it still decrease ~ 20% ( 80% -> 69%)

I try to do something, It don’t decrease percentage immediately but it become unresponsive after ~ 2 minutes.
I try to both charge it & turned it off, and after it seem not charging when it off ?
This is video record when I turned off already and started to turn on device

Thanks very much!

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