m5stick c plus battery will not charge

[Peter]

I bought a couple of M5Stick C Plus a few months ago and now I want to put them into operation. Unfortunately, the battery does not charge. A 68 ohm resistor between bat and 3.3 volts does not help either.
Does anyone have a tip on this?

The voltage at PIN BAT is 2 mV. When I connect a LiIon battery there, it will be charged.
Looks like a cold solder joint. Is something like this known. It is so with all 4 tested devices.