Can this door be repaired?
Inside the door frame is a tube like opening that runs the length of the frame. It is an integral part of the frame and is formed when the metal is extruded through a die.
The opening usually gets broken or is forced wider when the screw is turned to tight. Also corrosion occurs over time.
You can try this first: get a screw of the same diameter as the original, but slightly longer. You may be able to reach a sound section of the adjoining frame.
If not carefully separate the two miters until you can see an attachment point. This is not something that is easy and can be dangerous.