At the top of the sleeve part of the boom is a gear and that is supposed to turn against a rack of teeth all along the inner slide part of the boom extension, to make the boom longer or shorter.
However, it just spins but does not grab the rack. The inner boom piece slides back in under its weight without resistence. If I push down on the thing that holds the axle, I can get it to work as long as I'm holding it.
In the photo you can see I slip a piece of paper along the line where they should be meshing.
How can I tighten up the clearance/tolerance on this part in a normal Lego manner, rather than briging in other materials or modifying the standard shape?