It is part of the 3 in 1 flex cable. One end is what you see, the others go to the camera and the core board.
Make sure he gets an original DJI replacement. Otherwise the errors will likely continue. Also, “incompatible data error” is seen when a damaged gimbal is repaired with new parts, but the IMU doesn’t recognise them. I read somewhere that DJI need to run their “repair tool” to rebind the parts.