Oh, I think I found the actual problem:
The naming of the meshes is very, very important. If your model is named:
modelname
then your collision mesh needs to be named (assuming you want a convex collision)
UCX_modelname_xx (the _xx part is optional)
You have:
interior_walls.000
UCX_mothership_interior_walls_00
See the problem? I would try this:
interior_walls.000
UCX_interior_walls.000_00
or something even simpler if that doesn’t work:
interiorwallsA
UCX_interiorwallsA_00