New
#11
A good run of memtest to see if any bad dimms are present would be the best move so you can isolate and remove any. That will also show if any are present before touching the other system you know is working.
The idea is to either confirm or rule bad memory as the problem. Another thread lately saw a bad dimm when someone added more memory on and started seeing problems solved by bringing the bad dimm back for a replacement. Apparently all 3 dimms the original pair and the returned defective one were the brand and type as well as speed and timings there.