Had a bit of a positive development which I posted about here because I couldn't find this thread (even though it was staring me in the face lol)... basically put a 3rd video card in and it now works reliably still after 2 days in a row. It's still a temporary measure as the card I am using is faulty, however definitely an improvement, and is actually making me lean towards a PCI connectivity issue. time will tell I guess.