Asrock 6800 Can't Post With CSM Disabled

My rig has 3x Nvidia’s and 3x 6800s, (2 AMD, 1 Asrock), and can only run 5/6 GPUs.

When I plug in the Asrock 6800, it will not post with CSM disabled. I can only boot it with CSM on, but the problem is that my Nvidia cards get error messages if CSM is enabled. Anyone know a solution to this?

Motherboard is using suggested settings from the HiveOS guide

I have checked all the hardware’s and it doesn’t seem like there are problems with risers/connections.

Motherboard is a ASUS Z390-P with latest bios (v.3002 from 2021/04/19) .