Like Brad posted - the window doesn't go all the way down . This is a single arm regulator so the cocking bit probably has something to do with the channels on the sides being loose - worn . These are your basic fuzzy channels and if tight the window can't **** . The slot the arm slides in could probably use some lube also .
It uses the window regulator to pull the window down and push it up from one point that the glass could pivot on. The channel attached to the bottom of the glass could be loose on one side or there may be an obstruction on one side making the glass hang up. When all the way down there is still about 3/8 inch showing.
I have an original operator in mine and it works well, runs down straight and goes right out of sight. I expect either your channels are worn, as suggested or you have replacement glass which may have been cut even an 1/8" too narrow.