How old is the line? What does it look like?
Rope clutches function on friction clamp. They pinch the line. Over time they compress the inner strands and the line gets thinner in the area of frequent use. Some of the strands even break.
Like in the 1-2 foot length of the main halyard you reach each time you raise the main sail.
And with friction comes wear and dirt. How long has it been since you cleaned the rope clutch?
Perhaps you are due for both. A cleaning of the clutches (I assume you have more than one and a change of the halyard.
Some folks choose to flip the main halyard end for end, or cut off a foot of the halyard where it connects to the head of the sail so they move the damaged section away from the clutch. But this is a fools solution. If damaged, the section is now somewhere in the middle of their halyard run.
Only you can tell if this is a good solution for your boat.