As the title says, I was using UE4 4.12.5 when the autosave started… and apparently I ran out of space on my C: drive. The Editor crashed, and now I can’t open my project anymore, it closes every time.
you can try to delete the derived datacache, empty a bit your c drive and relaunch your project.
it can be long to rebuild the DDC on big project, so you may need patience 