thank you for all the feedback

first we have  220v in europe
thanks for the idea but i can rule that out

for both problems it helped to flash the S17 recovery image, latest version from the Bitmain  website

https://file12.bitmain.com/shop-product/firmware/c2c32666-d4ab-49b7-870f-9a31b46074b7/2020/09/27/10/sd_set_default_password_enhanced_0527_S17.zip

Prob 1:
After flashing reset to factory default, then connect the hashboard that solved the more "than 0.5v diff" probs.
Then update to latest firmware 


Prob 2:
still exists but one of the 3 hashboards is now  recognized while the other two still say 0 Asics found

I do not know if this has to do with the flashing it worked afterwards
After this I checked the cables cross all boards with all cables but noch positive effect.

All boards have the same product id/pcb so any further ideas?