If I understand the problem correctly, this seems to be typically what is referred to as "tunnelling", i.e. solid objects moving at relative high speed going through each other.
This can happen if the size and speed of Bob and Bar, and the framerate, are in a configuration when at frame n Bob is totally above the bar, and at frame n+1 bob is totally below Bar ; in this situation, Bob and Bar are never really in collision, since they move too much in one single frame
The usual solutions are time slicing (moving multiple times in smaller increments in one frame) and continuous collision detection (CCD, using swept volumes), though I'm not sure how you would solve this in C2...
You might try using a bigger hitbox to detect possible tunnelling, and then the accurate hitbox, in case of possible condition