Well, a few thoughts. But this is a common issue, and sometimes it has to do with 30-year-old equipment.
Almost all mainsails resist hoisting the last few feet. This is true even of boats who have installed the (miraculous) Tides sail track system. I still have to use a winch for the last feet, although the rest goes up hand over hand. Yet Tides sails fall like pianos.
Sometimes there are multiple shackle leads on the headboard. Sometimes the angle to the sheave can be improved by changing leads.
Sometimes the track is at fault, esp if sections of it have become misaligned. Sometimes the slugs have worn out or lost their ability to remain oriented.
The masthead sheave is often blamed. I think it is less often the cause, even if jammed. It shouldn't delay lowering much.
Sometimes full-length battens worsen the issue, since they put big pressure on their dedicated slider.
It;s always hard to lower a mainsail downwind, and easier to make it luff some first. (With Tides, yes, I can lower dead downwind, but it often takes going to the mast and tugging, since once started the sail lays on the spreaders).
Some folks rig high downhauls to help lower a sticky mainsail. I happen to be dead against that, because a sail that won;t come down can be quite dangerous even in common scenarios. A thunderstorm approaching, for example. And the solution to a stuck mainsail usually means climbing the mast.
The Tides sail track system is universally celebrated here as a solution, we can do the installation ourselves, and is relatively cheap as boat stuff goes.