Collisions not working with RIGID

Maybe i'm doing something wrong, but in my little TGB pinball game, collisions work fine when the ball's collision mode is set to BOUNCE. If i switch it to RIGID, sometimes the ball collides with the walls and flippers, sometimes it doesn't. i can hit the same flipper or wall and sometimes it stops, sometimes it goes through

Is this a bug in the RIGID setting for collision or is their something special you need to do to make collisions work with RIGID that you don't need to do with BOUNCE?

-baylor