I'm getting duplicate MIDI notes when recording. The general solution I've found for this issue is to turn off MIDI Local. Cannot find anything about it in the manual. Maybe it's called something else than MIDI Local for this device?
Thanks for your reply Reefius! I think you where on the right track.
Meanwhile I've been in contact with the MOTU Support. I needed to activate simultaneous recording on several MIDI tracks, in DP called Multi Record. That way I could choose the right input source. Recording is now working as expected without duplicate MIDI notes.