If your controller is not sitting correctly on the boiler, the lugs need to be moved into the row below.
This will raise up the controller and it will sit in place. The box is held firmly in place by the lugs, then it sits on to the metal bracket, not in it.
The bracket is there to protect the wires underneath the controller. The lugs have two rows so the controller can fit the Original G30 controller as well as the bluetooth G30 controller.
Please unscrew and move them down one and this will solve this issue. Refer to the page below, found in the instruction manual for more detail.