As far as I know, trigger/momentary behavior for live.button and similar objects is not yet implemented. Leads to MIDI/key mapping and automation problems in Live.

Known workarounds include sending a bang to button immediately after it's been pushed.

Case of mine - a button set to bang from both transitions, mapped in Live. I want to press a mapped key/control, lighting up the button, receiving first bang, and then have it faded upon releasing key or control, receiving second bang. Just like the mouse clicking behavior. Any solutions? Workarounds? News on further implementation?