OK, fixed it. Prawn-X is back alive! 🥳
Turned out the battery was completely flat. After disassembling, I measured 0.00 V between the pins! I do not know how that happened, maybe I did accidentally leave the device on when putting it away. Still, I'm pretty sure the battery should never discharge to 0 V in any design scenario, as the device should automatically switch itself off before. I guess this is related to the "battery protection bug" f(x)tec keep mentioning in their updates ...
Anyway, I was able to charge the battery to ~50% (3.9 V) using a laboratory power supply. After tha