Why can't I plate consistently when the pressure is on?

You already know how to plate well. You have proven that in the quiet moments, with time to think. So the gap is not skill. The gap is what happens to you when the ticket printer speeds up and six plates are due at once. What happens is this: you stop following a method and start reacting. You reach for whatever looks right in the moment. Under calm conditions this works because your instincts are sharp. Under pressure your instincts narrow, your hands move faster than your judgment, and the plate that comes out is whatever survived the panic — not your best work. This is not a flaw in your character. It is what happens to every cook who has not built a fixed sequence to fall back on. Fix the sequence, and the pressure has nothing to unravel.