We have all thrown away board bags because, when we tries to free the salt jammed zipper with a pair of pliers, we trashed the zipper and rendered the thing useless. Garage is full of dead board bags. Fear not, there is a solution. It works - as unlikely as it sounds. I stumbled onto this solution when I accidently spilt some Bushman's Friend on the dinning room table only to find that it disolved the varnish and left a serious blemish. Truely a powerful solvent. Works with Airoguard as well. Just spray some Airoguard on the jammed zipper, wait a few moments and voila - zipper slides like a shop bought one.

Or as above and a squirt of WD40.
If you stuff it up with pliers its $2 for a new slider at a trim shop, cut a few teeth out and slide it back on.

What the hell is Bushmans Friend though?? If you mean the insect repellant it dissolves plastics so might be more likely to damage the zipper ...?

I use parts oil or wd40. Whatever is closest.

www.bunnings.com.au/inox-300g-aerosol-lubricant-can_p6100723

Can't fix mine, even tried brickies acid. Not happy.

Never had a YKK zipper stick. Must be the bench mark for quality zippers. If I see these on a board bag or the like, I know it's going to be a decent product as they have obviously used good parts in it.

Have had plenty of other types of zippers get stuck though.