As it turned out, the triangulator only works fine for regular polygons, but creates incomplete meshes for sectors with multiple sections or some degenerate areas, which are quite common with swinging doors.
The node builder is more costly and creates wall splits, of course, but it does not create broken output for degenerate sectors so it's a good fallback.
SO's vertex interpolation does not use the common framework so it got missed by the sector retriangulation checks.
We need to check two wall positions as well to make sure that sector movement is properly detected.
