Event not dispatched when in a callback

Hey there,
I love your product.

I am making a MIDI learn tool for observable (mapping any MIDI controller with knobs to sliders).

I think it all works well except, when I MIDI learn (see demo, you need a MIDI device) the event is not dispatched and the button value learned is not updated.

What am I doing wrong? https://observablehq.com/@nicola/midi-learn

Edit1: added a more specific example: https://observablehq.com/d/ea79910d428d9e37
Edit2: added a second example in the first observable where I show it still does not work as expected when using async/await and promises

I resolved it by putting a div around the button and let the div.value being updated and the event dispatched.