My -10 is in the paint shop right now, and they were cool with me doing an inspection and double checking SB's while the control surfaces were removed. Anyways, we found 2 sheared rivets on one of the rudder stops. And since 2 were missing, it rotated inboard. I suspect this is more common than not since the rudder will flap in the wind on the ground without something preventing it. See attached pic.