Whhhat, Dealers with fitters???
Sureley they should be tecnichians!! I've fit many a window but only after checking that the ironmongery is servicable. Many's the time yr actual customer implies the window broke all on its own & "we only need the glass". When ya get to the job, the trained eagle eye tech spots the bent hinge which touches the cab frame way before the window closes!!
I did however spoil a back window once while fitting a hedgecutter, Oops, left the window open while operating the controls through the door. Anyhows, at least he could see his shiny new machine through my clean new glass!! ( Always sit on the seat when operating etc.....)