GPU Memory Full when Main Display GPU selected

My Setup:
Dell R750 (x2 Xeon Gold 6346, 256GB memory, 4TB NVME)
x2 RTX 5000 Ada GPUs
RHEL 8.4 with Nvidia 550.67 drivers
DaVinci Resolve Studio 18.6.6
DeckLink 8K Pro (outputting to a 4k monitor currently)

Both RTX 5000 GPUs show up in the GPU Configuration tab. One of the RTX 5000s has the label "Main Display GPU", while the other RTX 5000 does not. With the "Main Display GPU" selected, I get "GPU Memory Full" errors along with green frames appearing in my DeckLink output. When I unselect the "Main Display GPU" RTX 5000 and only have the other RTX 5000 selected, all my problems go away and everything is buttery smooth. These "GPU Memory Full" errors show up no matter what - including on a fresh project with a blank timeline. The actual GPU memory is under 1GB (checked in nvidia-smi).

tl;dr Main Display GPU selected = GPU Memory Full errors and horrible performance

Main Things I've tried thus far:
- Different set of RTX 5000s to remove variable of a faulty GPU
- Nvidia 525 drivers and a few other versions
- Complete reinstall of OS and DaVinci Resolve

I'm running out of ideas for what can be causing this. Any suggestions would be appreciated.

[Peter Chamberlain]

Are your UI monitors all on the main GPU, as they should be?

Physically remove the second GPU and make sure the first works. Then add the second.