3D model looks good in editor until its put on our avatar

So we have had this asset made for use with a specific avatar. When viewing the 3D model (the bicycle jersey seen in the uploads) in the editor, it looks fine. However, as soon as the jersey is put onto the avatar or the animation that the character uses is added to the jersey, it warps and looks way off.

Can anyone give a pointer as to what may be causing this error?

Thank you