I just worked through a bunch of annoying “Unknown Structure” errors (it seems something there is bugged, but I wouldn’t know how to replicate it). I got through that by opening my two structures and saving them, then going into every blueprint and function that uses them, refreshing any nodes that use the structures, and compiling and saving each one. Now the only errors I’m getting during packaging are ones related to deleting files in the AssetRegistryCache folder. I haven’t been able to find anything at all online about this. Is it maybe some sort of permissions issue?
Edit: Eh problem solved, I should have just tried my idea before posting, but maybe this will help someone else. I went to that folder in Explorer and unchecked Read Only on its properties. That allowed the packaging to succeed.