I have conducted all the trials. I was able to run unRAID in legacy mode, tried another GPU (Saphire RX580), and ran the primary and primary and secondary GPU with vbios files. All with similar results.
I still believe it has something to do with how the unRAID is handling the address. For instance, my latest attempt resulted in disabling the parity drive (diagnostics below). For this latest attempt I did try running both GPUs and compare them in the log file when unRAID OS boots. They are similar but address 25:00 has this line in it:
Don't know what that