Power system hardware error. Restart aircraft (Code: 30210)

After replacing ESC pcb and flatcable, the Gimbal assy and multicore flex signalcbl and the mainflatcable without cam (cam pcb contains calibration data so kept that with drone and is also not broken I have a clear picture) and last in a desperate attempt even the gps pcb, I keep getting this 30210 error.
I measured 1 Ohm resistance in each motor star-winding, they all 4 do a 3 pulse movement on boot, so I exclude the whole motor part.
With DJI-Assistant2 I tried down- and upgrading in order to trigger factory defaults, downloaded .log and .dat files but they are encrypted and to be read by DJI-technicians only.
This leaves the main pcb BUT i do not know its partnumber or model number to search for on internet and so far prices are close to a complete second hand Mini2!
Is there anybody out there that can help me with my diagnosis ?

I have many photos but do not want to overflow your server :-)