I had a Hobie 18 that I bought new in the early eighties, Must have had the main up and down hundreds of times the first three or four years of use, never with a issue. I took up windsurfing and didn't use for many years and when I did it would get stuck sometimes. I finally figured out that I used to rotate the mast opposite the direction the hook was on to unlock and rotate a little to the direction it was on if I had problems hooking. I was just rotating the mast without paying attention to direction. It is very important to know what side your hook is on. On older boats owners will switch the side when the rivets come loose. Also different manufactures will have it on different sides. A low stretch halyard is also important as Bill points out. Twist in the line could help or hurt depending which way the line is trying to force the ring. If the hook is bent or loose can also cause problems. As I found out myself and others pointed out here if you are having problems, you need to see up there what's going on with the hook. Most cellphone are capable of videoing what's happening if you have someone to help record. The hook and ring method is a very cheap and effective way to secure the main. I have gone to a two to one halyard system with a swivel cam cleat at the base of mast because of several reef points on several of my boats though. There can never be too much wind, just to big of sail .
-- Tomcat 6.2
Supercat 20 / 17
Searunner 16 Tri home built --
This is what i use on my 5.5 - knot MUST face aft or i am struggling to get it on the hook and not getting the sail down without flipping my boat on the beach as the knot interferes with the hook
It's a yellow/green fluorescent colored line. that's about all I know about it, but it isn't very stretchy. I'm sure you're right about the technique as well. If the wind shifts just slightly or the mast isn't fully rotated, it just doesn't come off. I just need to keep practicing.