Buttons cannot act as a one-way toggle. If I try to program a button to ‘Undo’ in the Mod Looper, for example, the button triggers it twice - once on the way down and again on the way up. So I always trigger Undo twice with one press of a button.
This is not a new issue to the MDX, as the same thing happens with a MIDI controller button.
What is needed is a way to set up buttons (via MIDI controller or Mod Duo X) so that they only trigger on the way down.