Key gets stuck on "P"
 

After changing my shift knob, the car developed this symptom of not letting go of the key -even if it's on Park. Never did it before- so I'm assuming that it's due to me changing the shift knob. Is there a switch by the shift knob area that could be adjusted to make sure that it disengages the key upon putting the shift on PARK? The car is a 1990 300 E. The only way I can resolve it is by starting the car again, putting the shift down to Neutral and shifting it back to PArk with a little extra "umph"- just a little... then it disengages.

Thanks for the help