MY older SX Main gets very hard to pull when near the top, but like yours, it comes down very easily. I've repeatedly cleaned the sail track, and use teflon spray on the sail track, bolt rope, and pulleys.
For comparison, I hoisted a regular 18SE sail on the same mast, which raises so easily it feels like a different boat.
I added a pulley to the system, that is so simple to install and use that you'll wonder why you didn't do it sooner.
Since I upgraded the mainsheet pulley system long ago, I'm using an original boom block, but a smaller Laser boom block also worked.
Install a common snap hook to the 'base' end of the pulley, hook this to the center lacing, then with the halyard fed through this, you can raise the sail while comfortably standing on the ground in front of the crossbar, facing aft. The halyard line stays on the pulley all the time (knot in end is big enough to keep it in), so once the sail is up, unhook the pulley from the center lacing; it all stows in the tramp pocket easily.
I re-hook the pulley to center lacing when lowering the sail, if I'm standing in front again, so that the halyard leads to me correctly.
If you have to raise the sail while you're on the tramp (i.e. while on the water), installing a second pulley would reverse the pull direction to the rear, as well as adding even more purchase.
Standing in front while lowering has another advantage, if you prefer to roll the sail as it is being lowered (usually involves crew help);
Lower a section of sail, then use the 'Foot Cleat' * to hold the sail from dropping while you roll. This frees both hands for rolling.
Although this was 'treating the symptom rather than finding a cure', it actually turned out to be a cure (to another problem that I didn't know I had), as standing in front is so much more comfortable.
* 'Foot Cleat' - standing on the halyard while it lays on the ground.