Import 3D does strange things

I switched from Avatar Importer to Import 3D as recommended.

But it doesn’t work. When I try and reduce the height of a mesh the width changes instead!

I’ve tried every setting inside Roblox when importing and inside Blender when exporting.

Nothing seems to fix it.

Anyone know what I am doing wrong?

it’s normal, but easy to fix.
you can duplicate the mesh, and group it with its copy. then reduce the size of the model and delete the copy of the mesh when you have finished scaling it.