In "web speak", it is normally "PITA"......pain in the arse......

My comment sorta goes with another comment.....if the shaft latching bits are tight, the lock won't be in the correct place for a locking sleeve to slide.
If the sleeve moves freely when in the trailer, figure out why not when assembling......duh.....
One of the few times WD-40 dissolves old crap....but NOT a lube.
Wipe the control balls down a few times of the year (WD-40 is fine here), use a lube on moving bits, exercise quite a bit....be happy....