Chosen Solution
Zipper does not easily engage anymore & start zipping up, teeth all appear fine & the bottom is not excessively worn or frayed
Put a single drop of fine oil, like sewing machine oil on the zipper and open up and close the jacket a few times. Should become much more usable!
You might try chapstick on the zipper this is similar to a product that was out eons ago that our grandparents used to use I don’t find it for sale anywhere but it is very similar to chapstick hope that helps
