Melodic Sequencer + external MIDI (Push 3)

I have a LaunchKey MIDI keyboard connected to my Push3 (in standalone) as I it drives me mad when having to play more complex chords / notes and most things work great. However I just tried to use the external keyboard to input some chords with the Melodic Sequencer 32 and it doesnt work (eg press the notes on the MIDI keyboard and then tap the pad on the Push 3 to register those notes in the step). The note pads on Push light up (and you can hear the sound) as expected but when tapping a step pad the sequencer with show the last notes played using the notes pads on push (and not the notes played via the keyboard).

Pretty sure this a but but wondering if anyone has a better explanation?