Hei,
you can use command gpu-fans-find
to find the faulty GPU with his ID.
If its GPU 1 you could use gpu-fans-find 1
to find the specific GPU in your RIG.
Fans of this GPU will spinn up - thats how you find it.
Then you could check your riser → Use an other one. Maybe its working.
I didnt find a solution, only a workaround wich is working for some of my GPUS:
If im only setting mem clock and not core its working. (But only for some…)
One of my Rigs worked fine, after reboot same failure. Could not find something so its running without OCs…
Hope i could help you a bit.
Greatings
ReScUe