Use thread-lock fluid to prevent screws loosening themselves through vibrations.
If you wish to use it on a screw please note the difference between types: medium-strength "blue" can be released again if the correct tool is used. High-strength "green" adheres so firmly that the joint can only be released by applying heat, and with plastic parts this could mean that the joint really is permanent.
Use a Loctite pin to apply the correct quantity of either type of thread-lock fluid.
Thread-lock fluid high-strength, 10 ml