Hello, we are having this issue pretty often, the playout stops going "On air" even if it still shows like playing in the calendar view (little play icon on the show).
We've tried cancelling the show and creating a now one, deleting the current song so that it jumps to the next one, changing settings in the streams section so that it restarts the stream but nothing. The "scheduled play" light is on, but "On Air" light is still off. We cant find a way to sort this out from the GUI.
Only solution we found till now is to do a "/etc/init.d/airtime-playout restart", which is not good since only a few of our DJs can handle this sysadmin things :P
sorry to bring this issue back if it's already been solved or discussed somewhere else. I found a couple of posts related but not exactly the same.