In Iceland, my camera (Canon Powershot G5X) endured dirt, water, and ice, with insufficient protection. At night it was freezing, and I was camping in the backcountry. After several days, the camera became increasingly dirty. There was sand in the lens barrel mechanism and often the lens cover wouldn't close or open properly. During the final hour before it died, the auto-exposure would have a severe dark bias, proposing to make much darker pictures than it should. Then the camera died. The lens was in extended form and wouldn't move anywhere when I tried to switch on the camera. Instead I got the error message: lens error, shutdown camera, camera will shutdown automatically.
I sent my digital camera for repair to Jessops (UK camera store; my attempts to fix it myself failed). Jessops charged me for the diagnosis, sent me a quote (£450 or so) for the total, I declined as I found it too expensive, I bought a new camera instead. I have received the old camera back. Very surprisingly, it's working. Still dirty and can clearly still hear that there's sand in the lens, and at times the lens cover still has hiccoughs, but it's taking photos.
I have taken a series of photos varying aperture size, exposure time, and focal length; see this flickr album. To my amateur eye those photos look quite OK, but I may not be looking at the right features. Do those photos show clear evidence of a dirty lens or otherwise damaged equipment? How is it apparent that they do or not?
More photos in this flickr album