This is a page directly out of my Clam X300 owners manual. They recommend a gel product called Zipper Lube. I bought some online.
Fish Trap FAQ’s
Find parts and accessories at http://www.clamoutdoors.com
Q: The zipper on my shelter freezes up and/or sticks. Is there anything I can use to help prevent this from happening?
A: Yes, there are a couple of zipper lubricants available that our customers and pro staff have used with good results.
• Zipper Lube is one brand, often found in the camping section of sporting goods stores. This is a gel applied to the zipper.
• There are also a few silicone sprays that may be used to lubricate the zipper.