If you think of 5 bar gate and you removed the bars you would expect it to drop, we use the glass like a bar and pack it from the bottom corner next to the frame, to the top corner away from the frame.
1.The glazing beading must be removed, and the double glazed sealed unit must be in place, and resting on its plastic setting blocks.
2.The door must be raised on the lock side, to square it up again.
3.You should notice a gap between the sealed unit and the door, this is where the plastic packers are inserted (see image) to brace across the glass to stop the lock side of the door dropping out of square.