Didn't have a problem with zippers, but this past Feb. one of the cinch straps on the front of our Adco cover tore from the cover, ripping a large hole in the cover that I figured was un-fixible. Cover was just under 16 months old.
Contacted Adco, started warranty claim, sent the pictures and info they requested. Claim approved, and two weeks later had a brand new $400 cover delivered. Only cost was $35 bucks for shipping.
I wouldn't worry about your broblem. If you can't fix it they most likely will honor the warranty
Grumpy