Vega 56 MEM wont work again at 950 after trying other OC Settings

All worked fine with my 8x Vega 56 / 64 Rig. Stable at arround 51-53 mhs each and all 950 or 960 MEM.
I added another card today. All fine. New card worked all day at 950 mem stable.
Then i tried some other oc settings at a different GPU didnt worked out. So back to old settings, Since then the new one wont run at 950. TRM says: GPU detected dead. Now i can only run the new card at 910 MEM.
DONT worry about:
Riser double checked
Power double checked
BIOS double checked

all is same as before. But still 950 MEM will crash TRM.

Any ideas?

Cheers