When a click handler fires twice and nobody saw the second attach
The button looked innocent. Continue, in the enrolment office’s own type, sitting at the bottom of a form that had not changed in months. Applicants tapped once, waited, tapped again. Two records appeared in the office queue. The team that owned the form had already searched the click handler on the button. There was one. It posted the form. It did not post it twice.
The second attach lived in a layout. An older campaign page had registered a document-level click that fired a confirmation when the target matched a selector. The campaign page had been removed from the navigation in March. The layout had not been. On a slow morning the first tap posted; the confirmation handler, still listening, treated the same tap as a reason to post again when the response finally arrived.
We only saw this when the office sent a build that still included the layout. The first build did not. A reconstruction that starts from a cleaned staging copy will miss the retired listener every time. If you are asking us to explain a double fire, send the wrapper, not only the control people remember touching.