what kind of casings are you using, natural or collagen? With the latter, I always leave them stuffed in the fridge overnight, seems to do the trick. Also, if your mixins are too dry, the casings could have trouble sticking. Mix some water, or other liquid, with the meat, four or so ounces to a pound, should do it. Also, anytime you get air in the casings, you will have a section that does not stick to the meat. Use a needle, or sausage pricker to puncture the bubbles before smoking.
Not a bad Idea to get a kit, follow the directions and make your tweaks from there. I use Hi. Mtn kits, but have freelanced quite a bit too.
Here's a pic of some finished stix.