Hi Bronte.
Do you have an internal track that runs a bolt rope or bullets on the sail.
If you have slides that run on an external track,
check all the slides for wear or twist. You should be able to see a damaged or worn slide,
One bad slide is all it takes to bind the haul up. Replace any suspect slides.
If your track is internal I will ramble on and add one of my old posts.
Gary
Do you have bolt rope or slugs?
If slugs, check then all for attachment and damage.
Do you have an internal mast track or an external mast rail?
If it is internal it could be restricted at the choke point by salt, sand or some other build up.
To both clean and check the condition of an internal track I highly recommend the
AMAZING DOCTOR GARY'S FREE TRACK CLEANER.
You need about a foot of rough cleaning rope that fits the track pretty snugly.
Parallel to the rope you whip on a piece of lighter line that is 2 or 3 inches longer at each end (See Pic 1).
There should be an eye in each end of the lighter line.
The whipping will make the diameter of the rough cleaning rope even snugger in the track.
Connect the main halyard to one eye and feed cleaning rope into track. (See Pic 2)
Connect a light down haul line to the bottom eye.(See Pic 3)
Haul up a yard or so and haul down a few times then repeat as you raise the line up the track.
Pay attention to the spot where you think the sail is binding.
When you have cleaned the whole track haul the cleaning rope
down , spray it with track lubricant and repeat the haul up/down to lube the complete track.
Will take 30 minutes to make the cleaner and 30 minutes to clean and lube the track. I do it once a year as a part of maintenance.
Good luck