[parkher]

it was switched on and with a usb charger attached for an extended period of time (I still haven't fixed my broken (fallen off) on/off button). Then I noticed that it always switches on when inserting that usb cable, so I set it to switch off after 10 minutes.
While it was always on, everything was ok. But soon after switching off, this happened.
I think I charged it for a while while off. So the battery should not have been empty.
And the problem persisted when the charger was attached as well.
I don't know how smart the battery charging circuitry is, is it harmful for the battery or not to be continuously charged.
And, when the charger is attached, does the PB get all the necessary power directly or does it still get it from the battery?
Anyway, when the problem occurred, the battery should have been pretty full, I think.
Then I kept it switched off and charging for a while (probably then the problem occured), then 2 more days off and no longer charging. After that it is ok, so far. I let it switch off after 10 minutes and I switch it on by inserting the usb cable and then I take it out again when it boots up.

Maybe it got too hot while being charged while switched off, with its thick cover closed.
Previously it was continuously with the cover open (folded back) while always on and always charging - then there were no problems.
I just had it fixed to the sheet music stand with the charger attached.