Octatrack sending midi to Digitakt

If I have all 8 MIDI tracks muted why would Digitakt receive MIDI data from the Octatrack? We used my OT as Master Clock at a gig that other night. my partner’s Digitakt was receiving all kinds of notes and had to menu dive to the settings for blocking midi messages. I thought perhaps I unmuted a MIDI track and simply didn’t notice it. BUT the project for our live sets I use has NO MIDI Tracks. SO assuming I hadn’t turned on a MIDI track and all I set was MIDI CLOCK SEND, what other data would have been sent do you think?