By the way, forgot to say thanks for this great plugin, a4chitect.

Trev. (total newbie)

spp.skpRe thomthom's problem, this can never be solved, as the corner causing the problem has 4 edges/faces not three, so the program does not know which edge/face should be top priority. Only happens if lines meet at corner, as even a couple of pixels on one edge/face is enough to ascertain direction.
Hopefully the file returned altered will point this out better, one item prioritises the green face, the other the red. When the green is used, as seems to be happening when I tried it, you need to physically add a line to complete the edges/faces as shown in the blue faces in the diagram.
Hope this helps clear this up.

Trev. (total newbie)