Did you try other miners ? may be Claymore?
I've never had luck with running Claymore on a Windows machine always had stability issues.
What I don't understand is when it's a single card the hash is fine but when 2 cards are installed or more GPU1 is 0 or a fraction.
there are a couple areas to check...
are you using any riser?
how big is your power supply?
you state you have alot of ram, how big is pagefile?
the motherboard is it setup so the pci speed is the same for both cards? is there enough pci lanes in case one is 16 vs the other
try adjusting for slower dag load
-lidag Slow down DAG generation to avoid crashes when swiching DAG epochs
(0-3, default: 0 - fastest, 3 - slowest). This option works only on AMD cards
btw are you using discord overlay at all?
I've tried risers and with 2 GPU's on 16x slots.
I will need to check on the pagefile.
I'll try the dag.