a couple thing to check/do that probably won't help.. but you never know
Check for a possible updated vBIOS
Make sure you are running separate power cables from the PSU to each power input on the GPU
How are the cards temps? You could try down clocking the card and see if it stabilizes things or not
Do both of you use PCIe riser cables?
Are both of your motherboards BIOS's up to date?
Are both of you running the latest chipset drivers for your setups from either AMD.com or Intel.com? (I don't know your system specs)
Upping the fan curve help at all? Are all the fans spinning on the GPU?
Did you take some canned air to the card when you had it out? (careful spraying the fans so you don't spin out the bearings on them)