[LAU] Ubuntu 18.04 can't stop Jack from qjackctl

Hi all. I've been using Ubuntu Studio since 14.04, always run with Jack as the main audio server and generally never had any issues. Upgraded to Ubuntu Studio 18.04 and everything was fine for some months but within the last week or so I can't get the Jack Server to Stop from within QJackCtl, the application just hangs, making it quite a pain to change between using my internal and external devices! Any idea what may be causing this or steps to fault find the issue? Currently I have set QJackCtl to not connect on startup, so I can killall qjackctl, kill -9 jackdbus(pid), restart qjackctl, select correct config and start the server running. So I can get on with my work but obviously it would be nice if things worked as they should again. Regards, Dale.