Shifter bushings are also common wear items. Some combination of wear in bushings and mounts may have something pushed past adjustment limits. You might try disconnecting the shifter at the transmission and see if you can move the lever into the park position with your hand. Check all of the bushings and mounts while you are at it. Look for metal shavings or any other clues. After external causes are eliminated, service the trans and look for metal in the pan.