+1. Start by splitting the Instrument track, and see if you have control over the separate MIDI track echo, or possibly that isn't the track that's echoing. Technically, an Instrument track consists of one MIDI track and one synth audio output track, but it is possible to assign a second MIDI track after the fact to drive the synth associated with the Instrument track.
If all else fails, you can assign the input of that track to some unused MIDI port/channel.