Did you fix this yet? This definitely looks like a phono cable issue with the Turntables. I had the same thing happenning before I replaced the Turntable phono cables (the actual cables that come out of the turntable not just the external cables).
take out the cartige styli and clean the 4 little balls on it try to give it a lil lick dont worry its not dangerous if not check the cables that go in the seratobox having this problem since the dawn of time
@DillestJAMZ i am a beginner with this and have boiled the problem down to one of the decks either faulty phono cables or earth lead .....was just posting this vid to see if anyone else had the same problem