I have solved this issue in my case. What happened is that even though I was deleting DerivedDataCache folders (project and shared and global), there was nothing actually in those, so I wasn’t actually deleting the shader cache. I’m using 5.4 which now uses the Zen server to cache derived data. I opened the Zen dashboard from the Derived Data menu in the level editor and used the menu option to delete data and restart, and that solved all my weird shader compilation issues I’ve been having recently including this one.