There is no problem with those parts, but I'm TJ-Fixing the entire universe at the moment :)

So it finds the stud bottom edge touching the triangle edges making up the top of the (stud less) plate.

Also I don't know if you have your TJ stuff running yet but I'm running into a triangulation problem under certain circumstances. For example this:

C x-----x B
| |
D x |
| |
E x |
| |
F x-----x A

C x-----x B
| /|
D x / |
| / |
E x / |
|/ |
F x-----x A

Where c d e and f all lie on a line and thus no visible triangles are added. All goes fine when the winding is the other way around, but it happens fairly often. So yet another exception to add to the ever increasing list of things to improve.

For a quick fix I added a additional center point and added triangles to all others from that, but it's overkill for most of the splits. So now I'm searching for a efficient triangulation function that's best suited for the LDraw poly's.