I’ve been working on the scene on my teammate’s account as the error didn’t affect the scene when they opened it, and then I asked them to do some scene setting while I was away for a few days. It went well and they handed the scene back to me.
I decided to try and implement some possible fixes that Paul had suggested in an email he sent when he got back, but when I opened the scene and tried using Arnold everything worked. The OIIO error has just disappeared? Obviously there’s an actual reason but I have no idea what it might be. Morty didn’t alter any file paths or re arrange any of the folders and I didn’t change anything either before setting the project and opening the scene. I’m grateful it’s gone but I wish I knew exactly what caused it in case I run into it again.