My training partner and I were drilling TSC using the MTT book as our guide doing reps on both our weak and strong side jiu jitsu. After about 20-30 reps in the TSC, I asked him to try to push me off him, and he simply threw me forward a few inches and then got my back off his face and my butt off his arm I was sitting on allowing him to further push me down closer to his hips and escape TSC. Any suggestions on how to troubleshoot and stabilize the TSC position?