double check PSUs , i had recurring crash on nvidia rig , changed risers and tried countless fix to finally realise my problem was the cable feeding in energy the 1080ti.
My corsair 850 RMX cable with 2x6+2 pin can't feed the 1080ti correctly and rig crash every few hours/days, i plugged the same card with another 2x6+2 pin from EVGA SuperNOVA 750 G3 psu and rig hashing non stop for 30days+ now. Good luck !