What causes "Server not responded on share #?"

My rig has been running for a month without any issue until two days ago. Randomly, few times a day, GMiner log shows “Server not responded on share ###” on every GPU. It continues for about 12 minutes or so, then the watch dog kicks in to reboot the rig…

I don’t have issue with temperature, I have a moderate OC settings which hasn’t given me any issue, but tried various lower settings. I tried different pool, tried different versions of GMiner, but it’s still doing it. I’ve also tried updating to latest HiveOS, as well as reinstalling HiveOS.

Please help…

[gMiner log]

[syslog about the same time]

this happen after upgrade to 2.72? looks same with my case. Also no share notification. I’ll try to return back with gminer 2.71