You could make that assumption and then test it's validity by removing the DIMM or swapping it with another and running MemTest again.

After waaaay to long of a diagnostic process I seem to finally have found the defect ram module. It was not channel 8 as MemTest said. But was the DIMM slot reported by unriad. It was CPU 0 Channel 2 - That translate to DDR3_C1 in the MB manual. After pulling that out. It has now been running for 3 days, with no reported memory errors at all. :D

I have only skimmed the thread so sorry if this has been suggested earlier... But I have successfully corrected a RAM error before by re-seating CPU and RAM. Just a suggestion.

Hi @Alphahelix - I have tried re-seating the CPUs and switching all the ram modules around. But that still resolved in a RAM error after a few days, sadly. 

But many thanks for the suggestion 😃

@Alphahelix did you switch qround the ram also or just re-seated them in the same slots?

As an ex-Lab-Tech, I chose a methodical approach. So with reference to my motherboard manual I found the memory configuration for, per module setup and added first one module booted it, tested it, shut it off, then two modules. By the time I was done all modules was inserted and it worked. Or so it seemed, after a few days the error came back. I then re-seated the CPU's. now the error disappeared, for good this time. 

 

I don't know if this will fix your problem, but I do think its worth a try.