.fbx Import Issues

While I was trying to import an .fbx file of the city I live in, Roblox basically decided to rend the buildings and roads apart. When I split the meshes of roads and buildings into multiple sections, this happens:


Is there a fix to this?

Note: For anyone who is curious about the files, I attached them here:
3d_tynda_chaoticmess_nomap.fbx (1.9 MB)
Initial file:
3d_tynda.fbx (2.1 MB)

Turns out, this issue was already discussed here: