Main sail track problems

[westfifer23]

I have an old C27 and recently I am having difficulty raising the mainsail all the way ( about a foot short of the mast truck) so causing the sail to bag. The plastic sail glides look fine and I have used sailtrack lubricant which doesnt seem to improve help the situation. What should I be looking at the enable me to raise the main all the way?

[TrueBlue]

If your halyard is rope-tailed wire, check the wire - close to the shackle connection - for any fraying which may become snagged in the masthead sheaves.