This zipper stitch helps to prevent future wear by keeping the tape away from the edges of the slot. If your sail has full length battens and batten pocket end protectors along the boltrope, it will be necessary to remove those protectors before repairing the boltrope sleeve. I often sidestep this repair by simply hotknifing away the boltrope in front of the headboard. Secure the rope in its sleeve just below the board before you do this since you will probably cut away the hand work that previously tied the boltrope to the head of the sail. Check all grommets carefully.
Grommets can pull away from the cloth in which they are placed.
A proper fix requires removal, repair of the fabric underneath, and replacement. Removal can be difficult. Once the old grommet is gone a layer or two of Dacron can be sewn over the hole. If a larger grommet is used in replacement, the cloth patch is often not required.