Try to mine with only one GPU at a time, until you found the faulty one.
This method will take too much time, because failure appears every 6-10 hours. I hope there are easier and shorter diagnostics.
The first opinion is that this is a software error. The fastest diagnostics is the launch of another miner for a day. If other errors occur, then you need to check the power supply, the raiser and reduce the overclocking of video cards.