Our Superstar was grounded for a similar condition. When the most experienced flier at the club pointed out that if my son was making a low pass and the flutter caused the aileron to leave the plane this could make for an uncontrolled turn into the spectators and pilots. We had to rebuild the aileron torque rod tubes to get the slop out of the linkage. It has not fluttered since.

The short answer. A fluttering control surface has very high forces on it and can self distruct in a heartbeat. The resulting loss of control can be very dangerous. Flutter is when the force of the air on a control surface (or a whole wing for that matter) causes it to move very quickly or vibrate.

Check for looseness in your control surfaces and linkages. In our case you could take the ailerons and move them up and down 3/8 of an inch.

Dave