I tried to pop it onto the reflector but ist didn't work, the reflector just gave way. What can I to give it a bit of resistance?

You were right, it was a matter of force, thank you. When removing the motor I heard two clicks, one when twisting it and one when the ball joint popped off the reflector. But when putting the new one in place I heard only one click when twisting it. Now I'm wondering what happened to the ball...

I have just tried to remove them, They don´t want to move a millimetre. Is there anything else to pay attention to? Any screw to release, any knob to press? I don´t want to damage anything.

I´ve got the same problem. Both motors are not working. What direction would I have to twist them in order to remove? It´s a 2002 vehicle though.