I can't tell exactly what the condition that causes this error is, but it is probably one of these three things:
Collinear points appearing before triangulation
Points Very close to one another within Epsilon (Or near duplicate points)
Bowtie Polygons (Unlikely)
The error PROBABLY occurs during level generation rather than the final triangulation of the mesh, because clipper should eliminate all of the above conditions without fail.
I can't tell exactly what the condition that causes this error is, but it is probably one of these three things:
Collinear points appearing before triangulation Points Very close to one another within Epsilon (Or near duplicate points) Bowtie Polygons (Unlikely)
The error PROBABLY occurs during level generation rather than the final triangulation of the mesh, because clipper should eliminate all of the above conditions without fail.