
Knee pinned across their stomach, mobile and heavy.
Knee on belly is uncomfortable to be under. Your opponent's knee is driving into your stomach, they can switch to mount or side control at any moment, and the far-side armbar is waiting if you push the wrong way.
Frame on their knee and hip, not their chest, and turn into them rather than away. Small hip movements make space to shrimp, recover your guard or come up to your knees. Don't give up your far arm when you push.