fathomX not working with voltage on tether

I just got a fathomX setup for my ROV and I am running a 380V power line. I got the fathomX integrated with 12V applied to the ground and robot side. I have a 24awg, single pair twisted tether wire and when I power up the fathomX without voltage on the tether the link comes up perfectly. As soon as I put 380V on the tether line the connection drops out. The tether at the moment is 60’. I have tried a short tether of about 2’ and that worked when I applied 380V. However, with the longer 60’ tether the link only works when I turn off the high voltage.