Yeh, sorry, it made sense to me :s (at the time).
Imagine the battery insert pivoting around the yellow plastic at the top. If you try to wobble (pivot) it around that point while the clips are on, in normal operation there should be no movement.
I found that my insert WAS wobbling. If you take the insert out, and look at it as though your going to put batteries in (palm of hand, fingertips on the yellow plastic and base of the insert at the heel of your hand). I put cardboard on the section of plastic facing you near the heel of your hand.
Doing this wedges the batteries in the insert against the contacts and stops them jiggling around.
I gave up on this, as already stated, my battery box was taking on water (mayday mayday!) so replaced the insert.