Did you let the casings dry before cooking them? I'm not a pro by any stretch, but I will hang the links and let the casings dry before smoking them, or I'll go ahead and hang 'em in the cooker at a lower temp, like around 130 (I think - I would need to confirm that) until the casings dry.
Once the casings dry, then bump the heat up to cooking temps and introduce the smoke. Sausages done this way need to be cured btw. Once they are done (I do them to an IT of 150 or 155) I'll throw them in an ice bath to stop the cooking.
If I have wrinkled casings on any of 'em, a quick dunk in boiling water will fix that. When it's serving time, I'll either grill or smoke 'till they look like they're close to bursting. The casings will usually have a good snap.
I hope to have some time to make some sausage at the house before the summer is over - if you want, I can give you holler and maybe you can come up when I do that.