Transmission not in park error

Last week I changed my engine air filter.
I then drove my car to dinner and parked on a slight incline. I shifted the car into park and opened my door to get out. The car did not enter access mode, and I also heard an alarm. I looked at the dash and saw "transmission not in park". I then got back in the car, turned it on, and shifted from park to reverse then back to park. The "P" did not light up red. I was in a hurry, and assuming it was most likely a park sensor (from experience working on transmissions) I again shifted the knob to park, then released the automatic parking brake (which was still working fine) and allowed the car to roll back slowly. It rolled about half an inch before I heard the "click" of the parking teeth engaging. The "P" was now illuminated. I then opened my door and heard the automatic parking brake engage again on its own, and the error message went away.

The car has done this almost every time I park now, and every time I must repeat this procedure to engage the parking teeth. The dealership can't get me in until late June, so I'm curious if anyone else has had this issue as I can't find anything similar. Beyond this the car drives normally and shifts normally. It never did this before I changed the airfilter, but I can't imagine the two things being related. I've worked on engines a long time and I just don't think there would be a connection, but just in case I took out the airfilter, and refitted it, checking to make sure I didn't damage a vacuum line or something. Everything looked okay.

I also scanned the car and got an error for the park nutral switch, which makes me think either A: the solenoid for the parking gear has gone bad, or B: the computer is trying to incorrectly interpret a mechanical issue.

Luckily the car still has its CPO warranty which I'm told should cover transmission issues, but im hoping someone else has had a similar issue and resolved it?