OP-Z MIDI out not working on ONE track

Track 1 (kick) stopped sending MIDI out. For some reason it ONLY works when OP-Z app is running (on macOS). As soon as I shut down the app (cause it makes the computer really slow!) track 1 stops sending MIDI and even playing the samples (even though right now I am trying to use it to sequence other stuff so not using onboard samples at the moment). I checked the MIDI setup on the app and track 1 has exactly the same settings as the rest.

Can you think of any reason why a track would only work when the OP-Z app is on?