This is a playlist of two videos discussing how to diagnose and correct three common mechanical problems: bridge key alignment, G#/A screw adjustment, and crow’s foot adjustment. Both videos cover the same three problems. One shows how to bend keys. The other advises taking the instrument to a repair shop instead of trying to bend keys. Both give a good description of finding the problem, with close-up pictures and playing demos.
Use the icon at the upper right of the video to see the playlist index.