How to fix a plug socket whose screws don't hold anymore?
As tacky as it is, I have seen electricians use drywall screws to hold receptacles when the threads are stripped out. the sharp threads of the drywall screw will cut new ones into plastic or thin metal. If your screw goes into a brass insert molded in the plastic, you may be out of luck. Do be careful of the length of screws used, the sharp points will go into a wire with no resistance, shorting out your connections.