Sounds like the problem is now in a bent trunk.
As far as I can see, the trunk is not bent, everything is straight and level (i.e. both trunk walls and cb itself).
The trunk is not "square", rather, it has a narrower area near the "root" of cb (built up lay-up on each side, as a kind of a "wedge", leaving very small clearance, perhaps 1/32" each side normally) designed to hold cb relatively tight when extended. Cb itself is also widest at the top. Since the clearance is now non-existant, cb is stuck (in closed position) at its widest point, where it came in full contact with trunk walls.