hey guys i have a 67 bird and my drivers side rollup window is messed up.

It cranks up and down fine, although it will only go almost all of the way up and then the crank will turn freely and the window will not go all the way up.

So the the window won't close the last inch or so. I can push the glass up by hand and it will go up but then it sags back down.

do my regulators, or rollers or something need to be replaced?