I am very sorry to report that today's 10.15.5 update did not solve this issue, at least not for my config:
Mac Pro (2019)
16c
384 GB RAM
2 x Sonnet m.2 4x4 loaded with Samsung Evo Plus drives in Slots 4 and 5
Disappointing to say the least.
Theophilos, did the OWC with manual reassignment of the PCI pool work for you?