Tuning in kinda late... Yes, if the shift motor is positioned properly for 4high, and the shift rail is properly positioned for 4high, but the transfer case is in 4low, then there's an internal issue and it needs to come apart.
I think there's some more troubleshooting though... With the shift motor un-bolted from the t-case, have you tried cycling from high to low and low to high? Does the motor turn like it should?
-Joe