I agree with @FDS, your best bet is to stick with a DJI repair or replacement. The problem could be in the gimbal, the ribbon cable or in the controller board. That is my main beef with DJI, their stuff is all proprietary and pretty much designed to be not repairable, at least my is not. The ESC's are intergrade into the main board, if one of them burns out, you have to replace the whole board.
With DJI, there is no such thing as just replacing a bad ESC.