When closing the power window, right after the window hits the top of the frame, the motor/regulator starts to make a loud rapping noise, like the worm on the regulator gear is stripping.

Is there a limit switch or excess torque switch on the power window motor that has failed closed and is no longer shutting off the power window at the top?

I hope that's what it is and I can find it before I strip out the gear and have to replace the entire window regulator!