Missing GPU’s - Help please!

I’m trying to set up a new miner, everything as far as I can see is set correctly, I have 5 other miners that are working fine. On boot up everything seems fine but the. After a couple of minutes the GPUs suddenly get marked as “missing”. Sometimes it happens after a minute, sometimes after 10/15 mins. I have changed PSU, Cables, GPU and even re-flashed the drive but still happening. If someone can help/advise It would be greatly appreciated, I’ve been trying to sort this for over a week.

Hi,
Try to fix OC settings on this card… silicon?
Also change RIG (motherboard) for this card , and check…

Not sure what you mean by silicon? I’ve tried all different OC settings, I’ve got another miner with same card that works, I’ve copied the settings but still just stops after a few minutes and cards appear to be “missing”. They are seen when initially booted up