Door lock defective

Hello, everybody.

On Friday I wanted to close my passenger door as usual with a slight swing, after which it came right back to me. It turned out that the locking mechanism that was in the small metal box on the front of the door was no longer working.

With my Audi Coupe, I had the same problem when someone wanted to break the driver's door open, but I couldn't do it. He apparently hung out the rod with a screwdriver, so that the door did not open and close properly. At that time, I thought that the locking cylinder was broken, because the phenomenon sporadic, i.e. Sometimes everything worked, sometimes I had to grope around with the key.

I immediately thought that I could now remove the entire door panel. For the sake of caution, I first screwed away the said metal box on the front side of the door and looked if there might be. I'm a little out of my mind. The very small train alone was probably enough that the locking mechanism then worked again. However, I had to find that the pressed threaded bushings for the M8 screws were completely rusted. After that, I first turned out the screws on all doors and cleaned the threads and sprayed in with cavity seal.

Question:
Has either of you already had the same experience and if so, what could be the cause of it??