Thanks Martin.
I actually solved this problem shortly after making my post on the forum, although this was more luck than judgement.
I selected ‘A-Pro 2’ as the MIDI input in the Mackie Control (as advised in the Roland manual) and then unticked the ‘A-Pro 2’ and ‘A-Pro MIDI IN’ boxes (leaving only the ‘A-Pro 1 option ticked) in the MIDI port set up.
Works perfectly now!
Thanks for your help.