You’re probably talking about smooth wall flex, there. It has a spiral of flat metal inside the flex liner, and in theory collects less creosote, but several have had the same problem you did. I think that penetrating the liner with screws increases the likelihood of unraveling, but I could be wrong on that.
@webby3650 and
@bholler both do a lot of installs, and could probably give you better advice on that, but most here just use regular 6” flex, often with a blanket wrapper for best performance on a high efficiency stove.
On that important and related subject, what stove is this going on?