Absolute painful mining experience past few days

I'm currently mining RavenCoin using 2 rigs with the detail below:

• GPU: 12 3080s each rig
• Mainboard: MSI B360F PRO (18 PCI-E ports)
• Ram: 8G
• PSU: 4 Corsair HX1200
• Cable layout: 1 Molex cable per 2 risers, 3 GPU per PSU
• Overclock profile: Core 50, Mem 2000, Fan speed 85%, Power limit 295W
• Above 4G decoding: ON
• PCI-E Gen2: Gen1 will cause half of the shares to be invalid, switching to Gen2 will disable mining mode

Here are the problems, the first rig runs FINE with the above config BUT the second rig can only run with 11 GPUs. If I add the 12th GPU the driver will fail (no temps) and freeze the mining software

Switch back to Gen1, the driver loads up just fine BUT half of the shares are invalid with the message (check overclock setting), the problem still happens EVEN WITHOUT OVERCLOCK. Switch to Trex from Gminer with fix the invalid share issue BUT the entire rig will crash after 10-15 minutes

Any ideas ? This is really odd since both rigs are completely the same