I setup a simple simulation environment something like billiards. There are four circle balls (dynamic) and four box walls (static).
Simulation works... except one thing. Sometimes when a ball rest against a wall, it sticks to the wall eternally. The other balls hits the stuck ball so many times, but the ball never wants to separated with the wall. The only situation where the ball will become unstuck from the wall is another if another ball is rests against the same wall such that it hits the already-stuck ball.
Why does this situation occur? How can I avoid it?