I don’t have and Octatrack or a 16n faderbank, but I have read their docs a few times in the past
So…
If I remember correctly, Octatrack does not have USB-MIDI. You need to use the OT’s actual MIDI ports.
The 16n Faderbank should be able to send MIDI over USB and minijack simultaneously (as read here at https://16n-faderbank.github.io/).
Have you tried this setup yet?
- 16n USB >> Norns USB
- and also
- 16n MIDI minjack >> Octatrack MIDI In
According to docs, at least, that should work. You should be sending the same MIDI commands to both Norns and Octatrack at the same time. I do similar things with FaderFox boxes on a DIY Norns and other MIDI gear. Works well for me.