.Fbx import handled differently in old project, updated mesh distorts during animation

I have a multi part character in my project, separate arms, legs, hair styles etc (independent meshes attached to one cat rig).
I recently updated a few components, two chest sections and a skirt (I hide and show the parts at run-time) The modified chest pieces re-imported just fine but the skirt gets translated in a strange way, it looks fine in 3Ds Max, and it imports fine to a completely new Unity project but is in the wrong place in the original project, I tried importing with a different name, but still it is broken

Any ideas?

Does the mesh actually deform incorrectly, or only the entire mesh is translated in a strange way? Translation and deformation are two different things. Translation is moving the entire mesh, deforming is when the mesh is deformed incorrectly by the bones.

Can you explain “recently updated”? What were the updates you made to the skirt, added verts/polygons, changed pivot point of the mesh, updated UVs?

Can you explain “strange way” in more detail?

Maybe there is a empty game object or dummy/point node in Max that is getting imported, or should be imported.
Or possibly - the vertex influence in Max is greater than 4 bones per vertex.

Consider redoing the skin in Max. Delete the skin modifier, reset xform, collapsing the stack, reapply skin, re-associate the correct bones, fix the weights. Re-export.

SOLVED:

Quality settings were set to one bone in blend weights (Edit → Project settings → Quality), set them to two and the problems are all gone!