Glass Container Packaging Problem

I am currently working as a student summer intern in industry with a glass container manufacturer. I have been assigned to try and come up with a short term solution to a problem they have. The problem is that once a full pallet of bottles has been stacked up, the top layer of bottles tilts or shifts over to one side and destabalises. This causes problems with the customers as their depalletizers reject to pick up the slanted/tilted bottle row and they have to be removed by hand. I understand the simple science behind this problem as simply their is no force pressing down the top tier of bottles. My question is however, has anyone came across a similar situation or have any input into how I could stop them from shifting. I have a few ideas but obviously I cant implement huge changes to the production line!