Situations like this can be avoided if the annual inspections are done properly. Both the rudder and the seat pan must be removed to catch problems. When I was the dealer for a German company years ago I and the company were sued for a fatal crash where the flight controls under the seat pan were compromised. This happened because water had puddled under the seat pan and the ship was parked in a hangar with the tail elevated. The seat pan had never been removed.

Regarding rudder hinges, they are prone to corrosion from wing water dumping, flying through rain, tail ballast dumping and, especially, urine contamination. A friend had to replace the lower rudder hinge in his D2 due to corrosion.

Removing the rudder and seat pan annually is a must.

KS