We had the same problem...drove me crazy.
Changed a couple things and it seeems to be working much better. First we changed the block at the top of the mast to a larger Harken block..changed out the halyard to Spectra line with no inner core...and last we put a block on the underside on the tramp at the grommet to help with the angle. Also we straighten the halyard before rigging. All the mods have helped a lot with the knots. Good luck...