Bumping this just to add some details.
I had intermittent "key won't turn to 'OFF'" issues that kept the key from being removed and knew it wasn't a key/cylinder issue. That was proven by unplugging the shift interlock connector (I think that's what it controls, just forwards of the 4WD arm, smaller of the 2 white electrical connectors) which allowed the key to be removed.
Problem was that with it unplugged, I couldn't then Start the vehicle, it was locked in the OFF position until plugged in.... so the cheap-mans fix there was a failure.
The first "fix" I found was to replace the bushings, and that did seem to address the issue for a few drives, until today. Today I was running errands and had the issue crop up 7 times in a row as I made my various stops. I finally just left the trim pieces laying in the passenger footwell.... get home, search, find this thread (first that seemed appropriate for my issue, everyone seems to default to worn key/cylinder) and investigated. Indeed, that pin on the shifter was not catching the white plastic "hook". While playing with it, I realized that there was a tell-tale Feeling to this when shifting Out of park it took more than normal force to pull the shifter back. That's because the pin was resting on top of the very top of the white plastic hook, needing to Force it down to make it back into operational modes. Hopefully this will be something that helps others diagnose based on only a simple feeling.
I ended up using a small pry-bar to slightly bend the metal bracket closer to the shifter so there's more pin engagement. In testing this fix, I realized I still had another problem in that the white plastic part didn't like the depress all the way all of the time. So I pulled it apart and found that there are 2 electric bridges (spring metal), and one of mine had gotten loose and was resting on the bottom, keeping the slider from depressing. Put that back in place, hit the electrical contacts with some electrical cleaner and the plastic with some lithium (felt dry and raspy when sliding) and the next ~12 tests were 100% without failure.
Annoying little issue, reared its ugly head the very first time I tried to turn off the 4runner after buying it (but not 5 minutes later after I drove a little further). Hope it's completely resolved now... also hope this helps someone else shortcut the frustration of trying to diagnose/repair.