One of two pivot screw "headpin" is thicker than the other and it is sligthly uneven, so it was a problem to put that headpin in the hole in the roller bridge. Both pivot screws were not completely covered with chrome color, there was few millimeters of yellow metal.
3 rollers were stuck, and could not move.
I had to install it urgently didn't have time to send it back, so I sand it myself, and put some force on the rollers to work.
Now it is working, but I expected more from Schaller, this was really poor.