So, I'm not really great at making meshes, but I made an outfit in Nifskope by piecing together parts of other outfits, and it seems to work in-game with one exception:

If the NPC wearing the outfit is viewed at certain angles, parts of the outfit disappear, only to reappear if I change my viewing angle. It's always the same angles that make it disappear (generally looking down on the NPC from near their shoulder, or upwards from their feet).

What can I do to fix this?