Nitropad X230 throttles CPU to 1.20GHz and has charging issues

I bought a NitroPad X230 in late 2020 and for a few weeks I noticed that the notebook throttles the CPU to 1.20Ghz when a battery is connected and charging. Only a reboot without a battery will unthrottle the CPU until a battery is connected with a charging cable. The charging process does not work without interruption. The NitroPad X230 will switch from charging to fully charged in a very short time. The same problem occurs with other working batteries.
I have already tried different power supplies with 20V, 65W, 135W and connected to a ThinkPad Mini Dock Plus Series 3 with a 170W charger. A multimeter measurement also shows that the power supplies are working correctly.
The batteries and power supplies have been tested with another Thinkpad X230 and it works fine.

Does anyone have any idea what might be broken? I am out of ideas, maybe it is the motherboard? After about three years of use, this expensive notebook unfortunately seems to be trash.

That does not read good :confused: I guess it could be anything from a loose connection towards the battery slot to the little voltage control chip on its way out. On the positive side: As long as it works normal without battery, it should be diagnosable by a tech. No other suggestion, sorry. I just know I’m religious about using OEM chargers with Thinkpads, because Lenovo has a history being finical about them (just look at their miniscule barrel variances between generations).