Sometime the tab just needs to be taken off and put back on, to do that you just need to take the stitching off of the bottom of the zipper, take the tab off and redo it, (sometimes there is a metal clip at the end that you have to remove) , sometimes you have to work at getting it to go back on, and then I would test the zipper to see if it still works, some times the tab is bent or damaged and that is why it is misaligned on the coils, sew it back up (if sewn correctly you don't need to put back the metal stopper)