I do a couple different things to prevent this
first of all, for plain unbacked posters, I usually put a poster bag on top of each poster as a separator. I never put a poster in the bag unless I have a special reason. seriously, posters stored flat in bags is a danger because when handled, they almost always cause small creases or dings. The unbagged posters means plastic is not backed up to plastic - which slides against the other plastic, so I have avoided the slide.
when I go into the drawers, I make sure everything is set right and I NEVER PUSH THE DRAWER TO SLIDE IN BY ITSELF FROM FORCE. I gently close the drawer with my hand on the handle