My door opens all the way, but when it reaches full open position and the motor stops, it "retracts" several inches before coming to a complete stop. Sometimes, the weight of the door (I'm assuming) pulls it almost half way closed again. The screw drive turns when it does this - like it's "unwinding" a little after it opens all the way. It does the same thing when I close the door and push the button again to stop it half way... it doesn't stop like it used to but keeps rolling closed (after the motor has stopped). Is there a "brake" that is supposed to hold it? Or a "clutch" mechanism that is allowing this to happen?

 

Welcome to the forums.

It sounds like the door is too heavy. Possibly a weak or broken spring.

The best thing to try is to put the door all the way down, disconnect it from the opener and try to lift it. It should almost open by itself. It should not feel excessively heavy.