Compensation units, they were yours originally
. I've been running them very under-volted (between 1.5-2.5 TH/s) due to warm ambient temps, but I remember you saying there was some kind of issue with one of them, do you remember by any chance?
Oh I remember you now!
I suspect there is an issue with _all_ compensation units. They are KNC farm rejects/used and abused miners. It's totally luck of the draw if you get a miner that is both stable and performs well. You're probably better off keeping them and running them until they die.
Sadly I am not interested in Neptunes any more. They are far too cumbersome for my hosting environment and I now much prefer the design of the S5s and SP20s miners.
The S4 might be an interesting purchase though. How much are you asking for that?