This problems seems to happen randomly but mostly with the Channel Settings editor open. The four directional cursor disappears when hovering over the timeline ruler so I’m not able to click to a spot on the timeline while the song is playing. I have to hit the spacebar and stop the song and then the four directional arrows appear again and I can click around on the timeline to change the playhead position then hit the spacebar to start song, after doing this I’m able to click around on the timeline ruler again for a while until the four directional arrow cursor disappears again.
My work around is to start and stop the song to get the four directional arrow cursor to show up again on the timeline ruler.
Hope this helps find the problem