My patterns have changed loads over the years. I used to block on certain sounds, then on any sounds. It would be worse when stressed or anxious or in certain situations like using the phone or with family (my mother especially). I spent a lot of time working through my emotional issues and my speech improved. The patterns still fluctuate but it happens more when I'm uncertain, have some kind of inner conflict or anxiety. Sometimes it's just lack of attention to what I'm saying or how I'm speaking. The thing that helps me the most is speaking from the heart, and this has led to a lot of self-examination to figure out where my heart is, what my values are and figuring out how to be authentic in what is sometimes an uncaring world. Very often my dysfluency coincides with me trying to be someone I'm not, and when that inner conflict is resolved I speak much more fluently.