When one of vga down or disable or hang.
If use claymore just teamview reduce OC and reset program.
If use SRBminer when one of vga hash rate = 0, i cant use teamview cause it often make teamview network disable.
There is a watchdog that restarts miner when some of the gpu's hangs, but in some occasions it can't do anything if your rig freezes for example.
Claymore can't save you from a windows freeze too

Anyway, you can try to disable the watchdog with the
--disablegpuwatchdog added in .bat