I was out of the country for a while, so apologies for the late repy.
Radio is always turned off (so yes the issue has happened with radio off). As far as I can tell, it has never happened with no songs in the queue. another song was always queued to play next.
The way the issue is usually triggered is when I ‘Play All’ tracks, be it from my library or a playlist. I also encountered the issue on my Macbook Air + System output so it doesn’t seem to be tied to my setup.
Perhaps it’s an issue with the music files? Most of my music is in .aif format. On the other hand, I tried playing a song that got stuck at the end (by clicking play previous) and it went smooth the second time.
All in all I still haven’t found a way to reproduce it consistently, apart from the fact that it’s consistent in its inconsistency…