I mean is it possible that you PSU could be failing, Have you been monitoring the temps, it could be also that the unit is shutting the hashing units down due to over heating
the unit is in server room. Temp less than 30C. I checked the cgminer log, when it stop hashing it says socket connect failed: Connection refused. If I on/off again the miner, it will hash. If I'm lucky it can hash about 2-3 days non stop. later on it stop hashing. and the log says socket connect failed: Connection refused
Diagnostic ping/traceroute are all ok. no packet loss
I have upgrade the firmware to the latest one. this is Avalon 2 55nm