Lol, you know when your in trouble when you come to find references for your work and the top google hit is yourself. I think this should be known as the (Ian) Hoyler effect due to the number of his courses where the top hit for a subject is his own website.
Some more testing (I forgot to switch assertions on this morning) and the convex voronoi needed polishing a bit:
Its to do with getting double readings when a bisector enters or leaves a shape due to rounding errors (particularly common in parametric form equations ive noticed....). While the algorithm could be fooled into giving the wrong output, I dont think that case will come up (famous last words I'm sure). "I'm only an undergrad, I'm not paid enough to fix this...."