Since I got the 42.3 update, it's definitely been working a lot more often. Before, I would have to manually stop/start the recording every time before exiting and entering the video. It became increasingly annoying. Now it works 9/10 times.
Just checked and I am on 42.8. When I first got the dash cam feature (one or two updates ago), it seemed to work ok. Now, it virtually never works. How do you manually start/stop recording?