So, I disconnected the duet 2 wifi totally, removed all the wiring from my printer checked the wiring and could find only one spot where a power cable (the negative one) had been slightly chaffed. I never managed to get a connection between this spot end the end of said wire though.
Then I tested the duet 2 wifi as Ian suggested, something I should have thought of myself from the beginning and it worked. Only problem was a screw connector on duet that did not open properly but that was an easy fix with the help of a screw driver. After that I rewired every high power cable in the printer and it has been running for to weeks now without any problem. Somehow I must have managed to get a short although I did not find any smoking gun and from the little I know from mosfet they generally do not come back from the dead. Apart from the screw connector being slightly sticky I can't see anything wrong on the duet.
Anyway printer and duet are both working so thank you for a superb support.
Best regards Stefan