I'd just like to say that I really appreciate you leaving your original comments and following up when you're able to resolve problems on your own; it provides very valuable information for other users who are reading along.
If a widget defines no event handler for an event, the event "bubbles up" to the container card or contraption, and in the case of a card it can further "bubble up" to the deck-level script. Events which "bubble" still further are handled by default event handlers, if any exist. I take advantage of this in many of my contraptions because there is often only a single widget that can produce e.g. a "drag" or "change" event and putting all the logic in the contraption-level script where i can see it at once is slightly more convenient.
An existent but empty event hander "swallows" the event and does not give higher-level definitions a chance to do their work. I recognize that event handler "templates" can be a bit of a footgun in this case, but there isn't any way Decker can automatically distinguish "as-of-yet unfilled" handlers from intentionally empty event handlers meant to suppress bubbling.
I'd also like to note that re-pasting a contraption definition into a deck where the original has been modified will not update existing contraption instances unless the new definition has a higher version number.
Does that help clarify?