Change the puck UUID?

That's fine - dump() won't say anything because there's no 'code' saved - it's just data that's been sent to the Bluetooth stack. Although I'll make a note to see if any of it can be reconstructed.

On the other Puck, you could try:

var f = require("Flash");
f.erasePage((120 - 3) * 4096);
f.erasePage((120 - 2) * 4096);
f.erasePage((120 - 1) * 4096);

This will blow away all the saved code - it doesn't get removed when you update the firmware I'm afraid. When 1v92 is released it should fix any issues like that though.