All used zips in our products are quality SBS zips. Sand and dust affect the durability of the zips. Therefore, please clean them. Spray with silicone spray can help, but the zip must be 100% sand-free. Otherwise the sand will stick to the zip again.
You should be able to open and close a zip with little effort. Do not use force to pull a zip closed, see what is wrong. Usually there is too much tension on the fabric and this tension should be removed so that the zip runs easily again. It is also possible that there is simply something between the zip and it does not run smoothly. Remove the problem and try again.
