What is causing screws to loosen on a fuel metering actuator?

[Waterloo]

The screws... I don't know, my first guess would be an engine vibration causing this. Again, which motor, how many miles? Have you replaced the Damper on the motor? They are a 500,000 mile disposable unit and wear out. No reason for the screws to break, unless someone has been playing with the actuators and over tightened. Need History.