'07 3124 Rear Bed Slide

During the first trip out, The only problem was very small. On the 2d day I noticed that the left arm of the rear slide out bed was out of it's slot and hanging free. I don't know when it happened and there seemed to be no problem from the inside.
I put it back in place by removing a plastic strip to allow it to go back in place. I see the root cause seems to be excessive clearance at the end of the arm's pin when it is in the fully open position. This excessive clearance goes away when the bed is in the stowed position. I plan to add extra washers to take up this clearance, but wonder if this will cause a binding condition in the stowed position.
I would have already tried this, but haven't pulled it out of garage to open it back up yet.
My question is is there another problem that is causing this such as the bed not level or installed correctly?