I’m going through the same thing with my 6 year old. It was intermittent to start but is now constant. We’re also currently in speech therapy. We have also been given similar advice; allow them time to finish, don’t interrupt, plenty of praise etc but if anything it seems like it’s become worse. My child’s had a session using ‘Bus Talk’ to help with slowing down and it does somewhat seem to help but I guess only time will tell!