About missing triangles, that's I think when you import into Blender
Blender doesn't seem to like triangles with double-faces
it happens when there are two triangles sharing the same vertices but having different direction
When the importer adds a triangle to 3 vertices, and Blender notices that there is already a triangle there, it will remove it, not considering the fact that the new triangle had a different facing
Try not using blender

I don't have another program.
Wait, how did you bypass the transparency issue, Adrien, long ago when you imported my textured Sector 1 Beta Rome?
Maybe at the time I made everything transparent
If Dff drops all transparency info, then is your editor responsible for overwriting?
Maybe I could change the default transparency in the next version...
But enabling alpha test on everything can cause performance drops