Physics problem

Well we're making a game that uses physics, the fact is that this is sometimes imprecise, since we have four objects that are generated randomly and have to bounce off a rock you have to move in three directions, until the object reach the other side.

Our problem is that there is some specific objects with random sometimes they work perfectly but sometimes lose strength...

Thank you very much for this great community!!

You'll get a better response if you explain in more detail, and maybe post the .capx file.

The fact is the next, we have an object, that we put on it some physic propierties, and the first object go fine, but the next do strange things, and we dont know how to make it like a precise rule.

Thank u!