Major bug on UE4 4.12.5. Unable to open levels

I’m using 4.12.5. I just saved a map on this version, closed the engine, no issues there.

Then I tried reopening the engine, and now it’s giving me the “failed to open map file, map was saved with a newer version of the engine.” The map won’t load at all, and if I right click it, it gives me a Failed to Load Asset error.

I’m sure I’m using 4.12.5 to save it, and I’m sure I’m opening it with the same version, as I don’t have more than one version of the engine installed right now.

How do I fix this?