I figured out the SHRINK WRAP and heatgun we use, was melting the wax coating on the backing into the contour cuts, making it difficult to peel them out. Also switched to 6mil matte BriteLine -- which feels and prints way better.
I'd really like to learn how stickermule and other online sticker services make their products.
Shrink wrap? Wax? Heatgun? None of those has any part in decal production. You don't need to learn how Stickermule does things. You need to learn what everybody does. And what you are actually working with.
You print on adhesive vinyl, which comes on a carrier, usually paper, sometimes plastic. The carrier is coated with a silicone polymer. Not wax. For ordinary stickers there is no reason to use vinyl with air release.
If you are putting a clear vinyl over the print, you do not use shrink wrap. You use adhesive overlaminate. You apply it with a roll laminator. There should be no heat guns involved in applying overlaminate.
When cutting, the goal is to cut through the overlaminate and vinyl and make an indentation or very slight scratch in the carrier, but not cut through the silicone layer. If you do, you will cause the paper carrier to separate and come up with the vinyl when you try to lift the sticker from the paper. If you did use a heat gun on the vinyl in some part of the process, you would activate the adhesive of the vinyl, causing it to stick to the carrier it normally separates from easily.