Edit: This bug report may only cover a portion of the original poster’s issue since F3 didn’t seem to be working for him/her. With the help of the great cfillion, we narrowed our portion down to incoming MIDI data causing the Transport STOP to malfunction.
Looks like ""Send all notes off to all MIDI outputs/plug-ins" action is unreliable" is still a thing in 5.70
https://forum.cockos.com/showthread....05#post1929805