Arnold seems to have a real issue with rendering in the render scene or in a region once I load a displacement map across UDIMs. The maps should work fine with the %(UDIM(d setup, i'm basically transferring everything from rendering in Mantra to rendering in Arnold due to Mantra's excessive hunger for ram.It's really not the biggest scene in the world. but as soon as I plug in a 4 UDIM displacement Arnold IPR doesn't generate anything. I've set my geometry to only 1 subdivision iteration.
My CPU is a Ryzen Threadripper 2950x - 16 core - which should at least be able to handle a basic setup like this.