Why autopilot can disengage when boat speed drops too low

At very low speeds, an autopilot can struggle to maintain course because there is not enough water flowing over the rudder for it to steer effectively. It ends up overcorrecting repeatedly and may shut itself off as a result. Lauren experienced this at three knots, sailing downwind in a dying breeze with the spinnaker up. The autopilot turned off for the first time on the passage, and she attributed it directly to insufficient speed causing the system to overcorrect. This is a practical reminder that autopilots have a lower performance threshold, especially in confused or very light conditions.