Problem with air flow and a/c

The actuators go bad over time. They are simple devices and can be easy to replace. The "can" being entirely dependent on how they are mounted in each model car, not on the design of the actuator itself. They are not easy to get to in a Prius. See for instance this video:

There are 3 HVAC actuators in cars, these are:

1. Blend door (mix hot/cold air)
2. Mode door (where the air goes)
3. Recirc/fresh door (mix fresh and recirculated air)

The problem in you car appears to be the mode door, in Toyota speak the "air outlet control servo motor". It does not look at all easy to get to, as it is just under the top of the dash, on the driver side of the evaporator. We had a problem with this very part after they replaced our evaporator - they forgot to plug the actuator back in. Luckily the shop that did that repair acknowledged their goof up and fixed it.Otherwise it would probably have been many hours of labor. Just to plug it in.

There is a slight chance that your broken clock spring (the part of the steering wheel that lets the button presses reach the rest of the car) is causing this. If the wire is shorting on something it might be sometimes confusing the MFD control. If that was the case there is a chance that the MFD control might not work, then turn the steering wheel to another position, and then it would work. The clock spring is a lot easier to get to.

 

The gen 1 and gen 2 ones can also be easy to repair (simple cleaning, cost of some electronic contact cleaner if you haven't already got some), provided they have not been dithering so long as to wear through the tracks.

That's covered in this thread: No, that wasn't a mouse in the heater.

The outlet select actuator isn't the easiest of the three to get to, but it isn't the hardest either. It's on the driver's side, a bit higher up than the air mix actuator (which is the easiest). It's a bit harder in gen 2 than gen 1 because the brake ECU is a big ol' thing in the way. But I think that thread has some stories where it's been done.

 

Right. Been there and tried that with all 3 actuators on a 1998 Accord. Seem to be the same style actuators as in the Prius. Had problems with the 27 year old plastic retaining loops (the tiny ones that hold the Denso case closed once it is put back together) snapping off because they were so brittle they couldn't bend without breaking, and they need to bend to let the little wedge pass by. In the end repaired one, replaced one with a junkyard unit, and replaced the other with an inexpensive Chinese version. They all are still working a year later. The driver's side ones were trivial to get to, with the screws right there and not blocked by anything. Passenger side one was a bit harder to get to, with some disassembly needed under the glove box, and it took me a while to figure out how to unplug a few cables which were in the way (having never been unplugged - they were very reluctant to come out). That last actuator was mounted to a sort of plate and it would slide into the dash (not quite straight in, but mostly so) where it was fixed in place with a single screw and some metal tabs that engaged. Kind of like pushing a VCR tape into its slot (but with a more complex path).

In short, much better access to all of these actuators than on the Prius.

I also learned that one should not touch the recirc door on a car of that age. The foam rubber coating will crumble with the slightest pressure. Luckily the material beneath that held, so there is just a finger tip sized dimple in the surface and not a hole all the way through.