Thank you! :) Are you able to send a link to the 3D model you're trying to import? I'll see if I can fix the crash on my end.
I've fixed the issue on the development branch (and it should be ready for the next beta) - think it was due to some of the surfaces of the meshes not having materials assigned to them when the game expected them to. So the game will now show a warning instead of throwing an error if this is the case.