All the photos are of the top surface of the flap.  They appear to show damage to the skin that is localized to the area of the actuating rod, apparently suggesting an excessive load in the "downward" or "lowering" direction transmitted from the rod to the flap.  This skin damage does not appear to extend very far across the span of the flap; it appears to be limited to about four or five corrugations.  In addition there appears to be some damage closer to the leading edge of the flap.  I'm puzzled as to just what could cause this pattern of damage.  Is this damage consistent with an excessive aerodynamic load?  Is this damage consistent with a mechanical malfunction that does not necessarily involve an excessive aerodynamic load?  Take a peek at the photos and see if you agree with my description and let me know what you think could cause this.  Thanks!  S.

Thanks for the suggestion, however external control surface locks are never used on this aircraft.

Looks to me like a classic example of misrigged flaps or a microswitch malfunction. I would check the microswitches for function and do a thorougth inspection of the flap system, paying particular attention to the flap tracks mounted at the rear spar. If the flap system was operated outside of the envelope (white arc), flap track damage will be evident by wrinkled underwing skin or working flap track rivets. Oil canning on Cessna control surfaces is pretty common as the use of ribs in control surfaces to hold the shape of the airfoil is limited.