Photos? I'm not sure I'm picturing the problem correctly...
Typically if it moves and it should not, use gaffers tape (duct tape if you must) and if it's the other way, use WD-40 to make something move that won't.
That said, if there's a little piece of tape stuck on the tube, it could be getting caught in the mechanism, and preventing movement. Try extending the legs farther out, to see if you can get them unstuck?