I've noticed that my Garmin GFC 700 autopilot is 'hunting' on ILS approaches. To be absolutely clear, I mean an approach using a localizer with glideslope. It is rock solid on RNAV, GPS, and other approaches, enroute navigation, etc. I've tried using both navigation radios and it hunts more than I do when I fly manually, regardless of what the winds are. The descent itself is perfect; I'm only talking about lateral navigation here.
What would cause that behavior?