You can not fix this problem without opening up the a/c box. Do not spray any oil anywhere in the control unit. To get to the mechanism that causes this problem you have to open up the unit. There are 3 clips on the top and also the bottom of the box. You have to gently push down on the 3 on one side with a small screwdriver and push the black clips out just enuf so the stay depressed behind the tan outer box. Be sure to remove the screws in the back first.
then flip the box and depress the 3 clips on the other side downward and hopefully all 6 clips will be caught under the outer box and you can slide out the front plate. You will see the 6 or so mechanisms that hold each button in place inside. A white shaft is pressed down by the button and a small spring loaded prong will catch in a notch in the white shaft to hold in the button. Mine had this problem for years. I had to clean each brass spring with lock eze which is alcohol and grafite. Do not put oil in there as that will attract dirt and make the situation worse. I even cut the notches to flatten the shelf the brass clip goes into. I had to do this twice. A dry lubricant like graphite will make the pieces slide but not attract dirt as it has no oil it is dry. These brass prongs/clips need to have the buildup of crap removed with qtips and the cleaner and you should get the buttons working again. Let the unit sit in a warm place and the graphite lock lube stuff will dry and then clean it again. Hopefully the buttons will continue to work and reassemble the unit.
Removing the face is the most difficult and when it is open you can see where the problem areas are.