Short version: Previously had 6.10.3 installed, three nvme 1TB SSDs installed, post upgrade to 6.11.0-rc2, one dropped out. Backed out to 6.10.3, all three were available.
This motherboard has four NVME slots, currently three are in use, two connected through the chipset. Regardless of unraid version, all three are seen by the BIOS. Post upgrade, I attempted to move around the two P31 drives, slots #2 & #4, slots #3 & #4, slots #2 & #3, regardless one or the other would not be seen by Unraid (using 6.11.0-rc2).
MSI z690-A Pro
2x16GB DDR4 3200
NVME #1: WD SN850 1TB <-- connected to CPU
NVME #2: Hynix P31 1TB <-- connected to chipset
NVME #3: Hynix P31 1TB <-- connected to chipset
I'm happy to do another upgrade and provide any additional logs if necessary.