Bengals are typically a slightly longer or slightly larger size than a domestic cat so I would be looking at the possibility of a dislocated hip or as he has fractured a bone before that might also be a cause.
Years ago a friend's young domestic cat dislocated her hip joint & it would "pop out" every once in a while if she was jumping alot etc, something to consider when you're at the vet is to ask them to test out the hip joints & possibly take some xrays of both the hips & the leg.
