It sounds like you have tried disconnecting the brake lever from the controller and also bridging the controller's brake terminals together and none of this has solved the problem.
I checked the wiring diagrams and The Razor Ground Force Drifter version 3 and up has a momentary switch inside of its throttle. This momentary switch turns on and off a relay in the controller which makes a clicking sound. So it is possible that the momentary switch in throttle is working, however, the hall effect sensor part of the throttle is not working.
Here is a guide showing how to test the throttles hall effect sensor and momentary switch on a version 3+ Ground Force Drifter.