Grounding the audio wire of any video transmitter will reduce the bandwitdh that the transmission channel uses. With less bandwidth, there are less changes of interference among pilots.
If you are not using the audio wire we therefore suggest to ground the signal to ensure that no data will be sent over the audio channels. Simply connect the audio wire to any GND or V- pad in your quad.
The TBS Unify Pro V2 / HV / RACE are utilizing a very narrow area of the band, so if you are not sure how to do this, we suggest to just leave the wires as they come from the TBS. The potential for interference is very low using the TBS branded video transmitters.