I think I've found a bug with EVENT_RELEASE
if the mouse pointer moves quickly from 1 button to another the first button doesn't trigger EVENT_RELEASE
I do have some overlapping buttons but even when the first button is definitely not being touched, it never releases unless I go back over it (slowly).

Having the same problem with A7 here.

I confirm this problem: the mouse pointer must be at least 1 frame outside the button for registering a release event. If it's moved too fast on another button, the event is not registered. We'll take care of that.