To be honest I didn't wade through your code but programmed something like this recently where this issue came up. I left it in as for my thing I liked the aesthetic effect this caused.

for my project it was whare the polygon was being updated close to a object would bounce off it. It meant that effectively the update moved the polygon over the areas that would cause a bounce.

This was as the procedure meant that it would evaluate at one frame and not cross a boundary and so not cause a bounce. Then it would update the polygon and the position of the object and see if the vector between the old position and the new position crossed any polygon lines, if so it would then bounce the object. The issues comes up when the movement of the polygon was greater then the vector that the object would move.

I guess there are a few ways that you could correct your code, for instance if an object moves from inside the polygon to outside you then place the object on the polygon at the point ware it's movement vector would intersect the polygon. Or just inside. Then re-do the bounce caulations to give it it's new velocity vector.

I hope this helps.