Fix Corrupted Shape keys in Blender
I've come across this multiple times when loading models into UE4 and it used to scare me when editing shoddy model stuff in Blender. This took me 3 days a few years ago to figure out and I waited for the moment it popped up again so I could make an important video on it. Also when I didn't feel lazy.
If you're like me, you'll most likely run into this issue A LOT and it sucks. There are also no tutorials on it and all forums say to completely rebuild your shape keys. Screw those people.