This is common repair attempt at dealer. They say it's a cold solder joint, your theory of the button actuation causing the failure seems more plausible.

The other common failure of these units occurs when the auxilliary water pump gets crudded up and draws too much current. If the auxilliary water pump draws more than 1.3 amps, replace it before it blows an active component in the pushbutton control unit.

Have a great day,