I cannot imagine a "common problem" that would cause this. You may know that 4th (if this is a 4 speed and not an overdrive) is just a coupling, you could strip most of the parts out of the box and 4th would still operate.( I couldn't get the shifter to go to 4th)
I think I would pull the side plate and have a look. Did you really "reef" on the shifter to get it to move, or did it feel somewhat normal?
