The plate that contacts the stock should bed down, with the square cut-out clamping each side of the "Scissor thingy" to that it cannot physically pop out without removing the plate.
Effectively between the contact with the stock and the locking effect of the above, the Harris is a very stable, solid bipod that is used by the military and police on all sorts so will take a kicking.
PS....obviously bipods are for tarts but there you go.....
