Focuser – Where Is The Damn Friction Screw?

My focuser is a PrimaLuceLab 2,7″ Hybrid-Drive.

My problem is that with CCD, barlow and Diagonal the focuser slides during focus operation, so I know there is a friction screw somewhere, but there are many screws, on Google I found a blueprint of the focuser and I found the correct screw, so I tight the screw a little bit and I resolved, below there is a photo of the focuser, hope it will help others!