Anthem400 Interesting you raise this.
My drummer triggers our song Start/Stop from his Roland SPD-SX PRO.
We've chosen to use NOTE ON commands (Note ON 62 in our specific case). and assigned it to the Start/Stop Playback action in ST3.
We do not use iOS BLE MIDI, we use CME WIDI (wireless MIDI) for this (and other MIDI devices), as I've never felt iOS BLE MIDI was as robust (consistent, reliable, predictable, performant, etc.) as I required for live band use.
Every now and then (maybe once in a set of 40 songs) our drummer swears he hits his Pad to trigger a song Start and nothing happens. He does it again, and it works.
I've always put it down to either (1) an inaccurate hit on the specific pad designated (i.e. the pad did not register the hit), or (2) a double hit was registered which, because we're using the Start/Stop Playback action, means that the song would Start and then Stop.
I had also sometimes wondered whether it was because it more often than not occurs when we're at a rehearsal and often I'm manually selecting different songs in a playlist and we stop, start, jump past a few songs, etc. as opposed to just working our way through a Playlist without any manual intervention.
It has never occurred with any consistency, or a reliable repro set of steps, for me to investigate. Also, if it occurs, the drummer can see a song hasn't Started and can just hit the trigger pad and Start the song (again in his mind).