Autorotate,
I know the one you're talking about.I've seen Childflights Dauphin on the ground more than in the air.I've spoken to Eurocopter and what you say is apparently exactly the problem.Vibrations in flight.The first problem was to do with the yaw system on the autopilot.
Apparently it is a awesome machine though.It can do 160 kts with 2 onboard and half fuel.