Not quite sure if my window regulators are gone or maybe just worn. Put the glass up about 1/2 way then you can grab the top of the glass and shift back and forth/front to rear. Could there be something else I am missing. The window channel on one door extends down into the door in the front and on the other door in the rear. This car was a salvaged car that I bought from someone who had started to fix it but gave up. Not quite sure what was done. before I got it.

 

sounds like there off track, might need either to replace the channel rubber (bone yard 3 bucks), i drilled another hole next to the existing hole that holds the vertical channel for the forward door window run so it would have less of that play in the glass that u described,,,,,,,also grease the hell out of all the channels and runners and motor moving parts that you can get too,,,,,,,,,,

 

Every Rx-7 I have ever owned has done this, the little plastic nylon bushings that slide left and righ down the window track get worn out. Hell one of my cars was so bad, back when it had manual windows. You could push the window down all the way from the outside!

 

Make sure that when you adjust the window, loosen all of the bolts including the ones that hold the front track in place. Roll the window all the way up, you may have to help it up with your hands. While holding it up in the right place, tighten all the bolts down and you should be good to go.
hanman