Electric window problem

[Paulturbo]

After respray my windows were really struggling to go up and down.
I greased all the runners and the drivers one seems to be a lot better now, the passenger window seemed better too, but then it got stuck half way up.

Now all thats happening is the motor is going but not moving anything.
I can't really see anything going on, is there a part which fails or comes off quite commonly?

[Bigfoot]

The motors are clipped into the metal gear to lift the window up and down, normally the clips which hold it in place break if somebody has removed them in the past. It might not be engaging anymore if you can hear the motor turning in the door.

[Junglist]

The window surrounds have been bent, squashed or something when removed by the sounds of it.

[Mr Raider]

Swelling corroded dry outter window seals and tired motors are the main culprits, inspect seals and silicone grease them up. I replaced mine with new from Renault earlier this year and can notice an improvement without changing the motors.