[thenrie]

I had the same problem. I cleaned everything up very well, sanded and primered the tube, painted it, then tapped it back into place with a block of wood and a hammer (after I rebuilt the insides of the box, of course). Apparently the couple of layers of paint on the tube were enough to tighten the tolerances. My tube is solid now.

I would hesitate to use something like JB Weld on it. There may come a time you want to disassemble it. If you have to reinforce it, I'd go with Matt's suggestion of pop-rivets. Not a "stock" look, but it would work and it could be undone, if necessary.