Cut it out completely. Take to a taylor or try to do it yourself. If lt is cutting like a knife that will solve the problem.
My suggestion is along these same lines. I recently had an issue with a boot that was fixed by a shoemaker. He looked at it and 1-2-3 knew just where to stitch to solve the problem. His shop was full of luggage, and he told me he did lots of work on zippers, luggage handles and carry belts, etc. A shoe and luggage repair place might be able to fix that for you. Check the yellow pages.