Clara promptly burns her hand on a Thing. A TARDIS thing... made by the TARDIS for exactly that purpose.
I didn't get this the first time but it was not a TARDIS thing. It was the magna-grab remote used by the Van Baalen Bros.
So, development done, time to round it off. With a hearty fun-poke at the people who complain about episodes having a reset button by using a genuine Big Button. Only this one is NOT a reset button. The purpose of the Salvage Bros is surely to shout loud and clear that things are not quite as they were. The reset is partial, mostly, but not quite the same. We have moved on. The Doctor tries to do something clever, throwing the button into the time crack, before realising that this is the work of the TARDIS (in Wonderland, the button would be maked "Push Me"). She has set the whole thing up for her own purpose, and now is setting such bits as she chooses back.
The Doctor engraved "BIG FRIENDLY BUTTON" with the Sonic Screwdriver.
I didn't realize the magnitude of the partial reset because in addition to the brother being kind at the end I had missed that the "android" brother was part of the family picture at the end. He was missing in the picture in the opening shot.