If your GPUs are all 8GB, then there have been issues with certain pools due to Dwarfpool going offline. Basically it tries to dev mine and can't connect and then usually an hour later it crashes. I had to switch pool due to this issue. We are waiting for a fix from Claymore.
Yes it happened to us!
If you've never tried it, EthOS has a support channel. Have you tried to talk to them?
http://ethosdistro.com/kb/#support