Some meshes are not exporting in UDK format correctly

[vegz]

Describe the bug
I am trying to export some meshes from ME2 into UDK. Most of the meshes are working fine but for some reason, some are not showing up correctly. I have tried psk, udk, and importing it from blender but same result. It seems LEX is exporting some meshes wrong for some reason.

To Reproduce

1. Open BioP_CitHub in Package Editor (LE2)
2. Go to exports 11520 (Neon_Foor_Edge_Divide) and 11534 (Neon_Wall_1x4). Open them in mesh explorer and then export in udk format.
3. Open UDK and press "open an external package" on each files you made before.
4. Neon_Foor_Edge_Divide is missing its triangles/verticies while Neon_Wall_1x4 is not.

Expected behavior
The triangles and data of certain meshes would be exported with the UDK file.

Version information:
6.3 Nightly 1/9/2024

Stack trace
N/A

Other information
N/A

[SirCxyrtyx]

Oddly enough, this seems to be an issue with the mesh, not the export process. This is the Elements array on the problem mesh:

Note that the Material Index is 2, despite their only being 2 materials (so the only indexes ought to be 0 or 1). This is exported as-is, which evidently causes trouble for UDK. Changing that to 1 causes the tris to show up in UDK.