Toddler Bed mesh crumples in game

After a lot of trial and error (that required reinstalling blender twice) I have my custom toddler bed mesh skin weight painted and everything. I had it working in game, however the normals on the mesh were bad, and I couldn't fix it within blender, so I had to export from my other program and reimport. Now with this new mesh, it looks fine in blender and in S4S, but when I bring it in game, the mesh crumples. The rig stays the same and works, but the mesh is just a flattened ball. Why is this happening? I copied over the armature modifier information to the new mesh, and it's set up the same as it was when it was working with the previous version.

Images to explain what I mean (ignore the default texture): imgur.com/a/MF0veEu?