How to reload default ue4 mannequin animation blueprint

I imported a custom mesh to replace the UE4 mannequin. I’ve done this before and I know how to do it properly, but I missed a step and when I imported the mesh, it said:

                                                           "FAILED TO MERGE BONES" 

This could happen if a significant hierarchical changes have been made e.g. inserting a bone between nodes. Would you like to regenerate the skeleton from this mesh?

The step that i missed that caused this error was that I imported the mesh without unparenting the skeleton from the UE4 manaquin. When I do that, it doesnt give me this error and all is well.

Now for the fun part, I accidently hit yes, and then hit control S due to force of habit, and now, the UE4 manaquin, and all other meshes that use the default animation blueprint and all other default animations have their limbs bound to incorrect rig joints. The whole arm starting at the shoulder gets bound to the elbow joint

now, the manaquin itself is fine, I can move all the joints and nothing appears out of order, the skeleton file and physics file are exactly the same. The rig itself is also fine, all the joints and bones are in the correct places. This problem only appears in the animation files.

So I’m stuck, re-importing the manaquin doesnt fix the problem, and replacing all the animation UASSETS from a working file doesn’t work either. What do I do??