Laptop stays on for only ~10sec when battery is connected, fine otherwise (Lenovo ThinkBook 15 G4 AMD)

[wraster]

I have a Lenovo ThinkBook 15 G4 AMD (HLXB5 LA-M062P) that, when the battery is connected, starts up and shuts off in about 10 seconds, even when connected to power supply via USB-C charger. When the battery is disconnected, the computer stays on as in normal/expected operation (powered by USB-C charger input). I bought a new battery and see the exact same thing. My conclusion is it is not the battery itself but maybe some circuit or component involved in battery/DC-in crosstalk. I found a schematic but not boardview (request link below - sorry for the formatting, I'm not sure how to make an inline link). Does anyone have suggestions as to how I can proceed to diagnose, or high-probability potential culprits to check first?

Thanks so much.