I am trying to install a new actuator in the driver side door after the old one had its teeth stripped. However, i'm running into a problem when trying to reset the window.

I can line up the motor,guide rail and rear vertical rail, but every time I try to insert the rear nylon guide into the guide rail (by tiltling the window forwards) the glass window pops out of what feel like a front vertical guide rail. (I can feel but not see this rail) so the window does not rise correctly. Any tips or statagies to keep the front of the window in the front rail?

Thanks

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1995 E320 119,000 miles