Is one of my TPS sensors failing... Or something else?

2016 Prius Touring model with around 100k miles.
Replaced the tires at 65k and all has been well.
I'm trying to figure out if one or all my TPS sensors are failing or it's something else.

About 2 months ago, before a 300mi trip, I topped off the pressure on all 4 wheels to 37psi and it was around 65F ambient when I pumped them up. I like this pressure when the weather cools down and it gets up to 39psi after driving (I use 34psi in the summer).
I was driving over a mountain highway from the valley floor (300'msl) and over the peak (1400'msl) and then down to another valley (400'msl). On the uphill drive, the TPS warning came on and I pulled over on a turnout (shutoff the car) and checked the pressure - they were all 37 to 38 PSI. Started up and the TPS warning came back on. At the bottom of the mountain road, I got on the Interstate and set the CC for 80mph. At some point, the TPS want off and didn't come on again - until 2 weeks later when I made the same trip on the same road and the TPS warning came back on, and it was around the same location.
It never happened on the return trip.
I thought it was weird.

I topped off the wheels ago about a week ago, and it has started happening now when I am just driving around locally on the freeways.
It came on when I had my wife in the car, and she pointed it out right away while it was still blinking. I told her to wait and see if turns off. And it did, about 20 mins later.

I assume that the TPS uses air pressure and not wheel speed sensors. And I assume it will not show a warning until there is a 3 or 4 psi delta between tires or if one (or all) of the sensors drop below (I think) 28psi.

Am I due for a new set of TPS sensors?
Do the sensors detect when the pressure it too high?

The portable compressor I used is the type that I can dial in the psi I want, connect it to the wheel and press the button. It will stop when it gets to the setting. I checked it when it was new with 2 of my digital pressure gauges and it's accurate. And, when I use it on my Leaf (which has a dashboard screen that shows all 4 tire's PSI) and its displays agrees with the compressor when I finish.