Why? While Rolling Window Down, Halfway Down It Takes A 1 In Drop..

[Cruizer67]

I am in the process of replacing the door channel windlace and as I am trying to adjust it notice that when powering the window down, that when it gets about half way it takes a noticeable drop.. about an inch or so. Not sure if I am out of adjustment or still need to seat the windlace seal in the track better any one have any help on this?

1984 GT 5.0