Actually, I do have a similar problem with the sound. 50% of the time the application locks up when exiting and almost every time, the sound is gone. I have to change the TTS engine from google to pica and back to google to get it working again.
My previous version (Basar) did not have this issue. i do not recall if I changed SYS.TXT and did not investigate the problem yet but will within the next 2 days. I think I was locking the app or loosing sounds when simulating a route to test the Freeway services which was my priority then.