Sorry for not having posted anymore. Because my workshop was occupied by a restoration car, it took me quite a while to get access to the car lift again.
Passed week I unplugged the HVAC compressor, insulated both ends and put them back under the plastic cover of the battery. Fortunately there is no HVIL, only the two HV-leads.
I cannot have a large drive because the car has no valid immatriculation. But I could do several rides around the block and It looks like the ghost has disappeared. I can drive in forward and backward mode, even with half way pressed brake pedal and keep staying on the brake without any turtle or error sign showing up.
As guessed by some of you the insulation problem is in the HVAC compressor. Disconnecting does not produce any fault on the display, so I can live without Chademo-charging for a moment.
But there is still a question:
Is there already someone on the market who can fix these compressors for affordable money?
I know that It cannot hold forever, because the design still stays the same and I am sure, that the supplier did a bad engineering job on that part. Thanks.