side to side on the g500 is ment to be as it is a button press (one to the left and another when pressing to the right).
Though depends on "loose". Mine is has riggle room, but need to push a bit more to get the button to trigger. Though I found it enouing so un-mapped those buttons through the software.
edit: and this is besides the normal down press to trigger a button press or the scrolling of the wheel which is effected by the button changing the wheel from free scrolling or clicking per small movement.
Makes the scroll wheel more of a joystick given the number of different directions it can move in.