(Bug) Major shape key issue

Kind of hard to explain exactly what’s going on in a title.

So, once I parented the body of my character to a rig, the shape keys all broke for some reason.

Here’s the basis, which is still completely fine:

And here’s what one of the shape keys turned into:

It still kept the shape it’s supposed to do (make? change into?) (such as her mouth shape in the example), but it completely destroyed the rest of her face and right arm. Each shape key does the same thing, and when I change it to affect a specific vertex group it still messes up one of the affected vertices if it’s included in the vertex group. This also only applies to the shape keys on the main body, and not her eyelashes/eyebrows/etc.

I can fix the mouth shapes by selecting the specific area they change instead of the head as a whole for the vertex group, but the eye shapes are still messed up. Is there an easier solution to this? Unfortunately I saved the model multiple times before realizing this happened.