Fatal error in UE project builds

After copying and moving my project to UE 4.21, I’ve been unable to launch a compiled project’s executable without meeting a fatal error. I can play the project just fine if I run it from the editor, but that’s all. I’ve been watching the logs and the only errors come from a periodic LogRHI error, as well as warnings from content that I’ve already removed from my project. I’ve tried some cleanup, tried rebuilding every level, and looked through settings to find out if I missed something. I’m at a loss and Google is no help. Any suggestions?