Sat Nav Screen open manually?

[Loft in Spain]

Me again, sorry for the mini flood of questions, but I am using the search tools, and just have a few things to sort out on my newly acquired DB9 (2006, US spec)

Ok, I've taken the sat nav head unit out as it wasn't opening and closing correctly.
I've fitted the new cogs etc from the repair kit, and I'm reassembling it ready to put back in the car.

However, whenever I screw it together with the first cog in contact with the worm gear on the motor, it seems to jam, and the screen cannot be opened manually.

Question : Should I be able to open and close the screen manually when everything is screwed together? Or does the motor have to do the work?

Thanks

Edited by Loft in Spain on Wednesday 9th January 10:42