Upper right flipper only fires on a full button press: that's by design

On Monopoly the right flipper button has a two-stage switch stack: a light press fires only the lower right flipper, and pushing the button all the way in also fires the upper flipper. This lets you hold a ball on the lower flipper during multiball without the upper one lifting. If you'd like them to fire closer together, adjust the second switch to close a little sooner.