Check your bolt rope at the head top of the mast. I'd bet the farm that your bolt/luff rope is hitting the top before the ring goes over the hook. If so, carefully remove a cm or 2 of the bolt rope off the head of the main, allowing it to go over the hook, melt it so it does not fray and remains uniform, I'll bet your problem is/ will solved by that...(I had the same problem, BTW.).