This is by no means a perfect or complete list and I slapped it together in about five minutes of searching on the Cockos Forums and /r/reaper for "hung note" and "note off". I kindly ask that you just use this as initial evidence of a real problem, then do more comprehensive research to sort out the variants of it, any false-positives and user-error, and/or bugs that have actually been fixed historically. For instance, some people report the "all note off" action working to silence the notes, and others (myself included) find that action does nothing to help and end up doing crazy hacks. Check out the first link which is a thread around an entire video one guy made on how he works around the problem. For me and for others, that hack doesn't work.
On the Cockos forum there are lot of old threads on this bug that have survived through the years with folks continuing to chime in with recent versions, suggesting this is an old problem that still persists.
- https://www.reddit.com/r/Reaper/comments/8cy1cr/a_fix_for_stuck_notes_forever/
- https://forum.cockos.com/showthread.php?t=183737
- https://forum.cockos.com/showthread.php?t=208732
- https://forum.cockos.com/showthread.php?t=166479
- https://forum.cockos.com/showthread.php?t=206808
- https://forum.cockos.com/showthread.php?t=207958
- https://forum.cockos.com/showthread.php?t=185642
- https://www.reddit.com/r/Reaper/comments/8e4aof/the_endless_midi_note/
- https://www.reddit.com/r/Reaper/comments/58crf3/hanging_midi_notes_latest_version/
- https://www.reddit.com/r/Reaper/comments/8kfg45/note_stuck_somewhere_cant_find_it/
- https://www.reddit.com/r/Reaper/comments/5rsgkr/having_issues_with_midi/
Many of these threads include comments indicating they've just tolerated this problem indefinitely, seen this issue mentioned regularly in other Reaper-oriented communities I don't watch (Facebook group), and generally it's clear to me this a long-standing, common problem. I'm not suggesting these are all related to the same precise bug, but they all revolve around the common problem of hung midi notes, which is a problem that can and does occasionally happen with any DAW, but very clearly a problem that Reaper has a lot worse than other DAWs. For instance, lots of people say that once they switch to Reaper, they start seeing this crop up and don't know how to deal with it. I've used lots of DAWs fairly extensively over the years (which is why I love Reaper so much - it is truly exceptional) and haven't had a significant issue with hung notes since the late 90s in any of them, except Reaper which still has it in the latest build.
I absolutely love Reaper and am honored to help bring this to light and get it resolved. Keep up the great work.