Hi Craig, I had that issue. Lexus Glasgow wanted something like £500 for part only plus labour to change it plus diagnostic so the bill would be crazy!
I found through https://www.amayama.com/ a much cheaper unit (Toyota 88940-30100 - ACTUATOR ASSY, SWING GRILLE), while it was getting ready to be shipped I removed the old one, just to inspect what could be wrong with it, I took it apart, checked the motor, lubricated everything and installed it back to car and it started working, no idea what was wrong with it!!! It worked until I sold the car and I hope it still works!
If you decide to do it yourself, it is not hard but a lot of plastic protection under car needs to be removed and even front bumper unclipped or removed, again it is not hard and youtube videos tell you how to do it. Who knows, may be your unit is not faulty, just need to be taken apart. Service department in Glasgow never heard before that this unit can get faulty!