Playback for certain passages cuts out after note input

Sorry if this has been talked about before, but I'm having an issue where if I input notes on a score, playback for for other passages won't work unless I edit them somehow. The play button is still checked on these notes, but nothing shows up on the mixer for these passages, and if I click on the passage so only that instrument is supposed to play, nothing plays. If I select all the notes and alter them in any way, the problem fixes itself, or if I save and restart, but it happens so often and relatively randomly.