Ok, I think I have a better handle on what's going on. Apparently the miners don't like ProHashing's coin profitability switching algorithm. Whenever it takes too long for a new mining pattern to get established, that's where it seems that my miner is having trouble, and just stopping. Since I added the c=digibyte field to my script, all three miners are working without issue.
I don't know if it's BFGMiner, or ProHashing's algo that's the cause, but apparently I wasted $50 on another hub, lol.
Cool .. glad you got it resolved.
I tried the same but with zergpool for a few weeks but never any issue like yours. I believe we could blame it on ProHashing - every pool has its own set of configuration though.
Send it back to Amazon then! LOL