Check the frame "lip" where the cam rests. It's easy to bend that thin aluminum lip when extracting or inserting stuff in the pass thru. Place a straight edge (ruler,etc.) on the lip and bend the lip so all edges align.
The longer cams, or "tabs, arms" can be bought on line at places like
http://www.rvlocksandmore.com/ or at most RV dealer parts dept. Also check the cam for it's shape, they can be bent as well but it does take more force.