I have an additional theory about those terrible tempers. Angry taking uses a physical force that maybe overrides the diaphragm/vocal chord tension. I also believe that this tension comes directly from an automatic, unwanted valsalva maneuver. William Parry (SLP, mostly fluent PWS) has some good videos about it. After I started using the following 5 techniques and got mostly fluent, my anger has gone way down (disclose/voluntary repetitions, eye contact, exhale, begin slowly, enunciate)