Reply to Traktor Scratch vinyl loses signal

I've seen this pop up before but no actual answer that worked for me. I've got an A8 with vinyl timecode on my MBP. It seems that after about 10-15 minutes, the signal (bar next to the timecode analyser) goes to zero and it defaults to internal mode. the only thing that fixes it is either restarting TSP or unplugging the sound card.

I thought it might be the timecode vinyl so I've been using the 10 minute side for now, but it started again on this side. The signal bar starts jumping as it goes up and down, then completely goes. Any ideas? I'm on 1210s with concorde pro carts. I've also tried earthing on the mixer instead of the sound card. Not sure which is best practice...