No, I mean that the way collisions are handled is extremely temperamental. Basically the two bots are allowed to intersect, and then a force is applied to both to move them apart. If you were to run some quick tests in the program, between colliding bots, I think you would see some very different behaviors under exactly the same conditions. The amount of "bounce" between two bots is a factor of how far they managed to interpenetrate the previous cycle. The force applied is extremely picky about how strong or weak it can be. If it gets outside its "sweet spot", the whole simulation basically can explode in a chain reaction.