I have an assembly where I have two parts that slide back and forth in opposite directions. The parts are mated to other parts to keep them where they belong in the assembly, but there are no direct mates between the moving parts on either side. When I drag one of the parts (I will call it A), the other part (B) moves in the same direction, maintaining the spacing that existed at the start of the drag. However, dragging the opposite part (B) does not cause the first one (A) to move.

As I said, there are no mates between the two parts A and B that link their motion to the other, so why does it behave this way, and is there a way to stop this from happening?