Ah, I see. The worm gear has become stripped. I'm afraid this can't be repaired or replaced; you will need an all new operator. We can help, but we will need a picture of it out of the window.
When Tom said we need to see it out of the window, he meant the whole operator. We won't be able to replace that gear you're showing, because it's pressed into the body of the operator in the factory. Can you send a photo of the whole operator, including the arms?
That's the one! Thank you.