:update: I understand what you’re saying – coast settings shouldn’t correct sync unless it’s composite sync?
I tested setting coast settings to various combinations. With both set to zero, the TV is fine, but the camlink is unstable. With post-coast set to ‘1’ (pre-coast set to ‘0’), the image was mostly stable but would cut out intermittently (pre-coast set to ‘0’). With post-coast set to ‘2’, the image is stable.