Note: This seems to be just the buttons. Knobs and Faders work as expected.
repro: create any button. On the events page try and assign a midi Event to button...... does not work. However, assigning a Key command to the button does work.
Also, if you create and assign midi cc/channel to a fader or knob (working) the fader/knob value will still show on the button in the events page when selecting the button after previously selected fader or knob.
