Single line reefing can be a delight, until the friction become so great nothing will move. I was pretty fed up with mine, when I first go the the boat, until I realized the PO had left me a tangle. A simple problem, and easy to fix, but often overlooked because it is out of sight.
The problems is that there are blocks inside, and when these get twisted, they lock up. The twist is introduced by a group of turning blocks near the mast (different from this illustration), that guide the line back to the cockpit or to a winch. Every time the reef is used, their corkscrew arrangement walks a small amount of twist into the boom.
The cure? Look in the boom-end to confirm that this is the problem. If yes, go the mast-end and untwist the line by hand in the required direction, until the lines are straight and the blocks are vertical. This may take 5 or 6 turns. Chase these twists through all the way back to the cockpit, so that they are not simply stuck between blocks near the boom. Do NOT release the line from the end of the boom and try to fix the twist from there. Although that end is also twisted, that is only a symptom of the twist at the other end. There is no way for twist to sneak in from the boom end, and if you try to fix it from there, you will simply create opposing twists. The problem originates at the boom end and must be fixed there.
On my boat this must be done about every 50 times I reef. Not very often at all. But if you've waited years, or if the boat is new to you, look inside the boom.
[This image is from the PDQ 32 Owner's Manual, free in MS word if you request it via the contact form near the bottom of the right column.]