More than likely you have one or more failed actuators. Using a system compatible scan tool is the easiest way to identify any faulty actuators. The mode actuator by far is the most common to fail.

If you would like to try a system recalibration use the following procedure.

Begin with ignition off.

Locate and remove the HVAC B fuse in the rear fuse box. Leave the fuse out for at least one full minute.

Reinstall the removed fuse.

Start the engine and allow it to run for at least one full minute. Up to four minutes is okay. Do Not Touch anything during this time. Doing so will interrupt the procedure and cause improper operation. If a failed actuator is located during the process, the procedure will also fail to complete.

Turn the ignition of for at least 10 seconds but no more than 30 seconds. Restart the engine and test the HVAC operation.

Since you stated 75 and 90 degree settings I am assuming you have auto HVAC controls. When the fuse is removed and reinstalled or the battery disconnected and reconnected the display should default to 74 degrees. This indicates that the recalibration procedure has begun. So that leaves you with having faulty actuators. The mode actuator is the most common to fail. As stated earlier it is a bit of a guessing game to determine which actuators are faulty unless you have the codes and data looked at with a system compatible scan tool. The alternative is to remove panels and observe each actuator for full 90 degree arc movement of the actuator shafts. This has to be done immediately after cycling the ignition back on after battery power disconnect. There are five actuators that will be recalibrated. If any one fails during the process the procedure will stop and not advance to the next actuator to be recalibrated. So figuring out which one is acting up will be key to fixing your problem.