A few thoughts.
Have you confirmed that range mode is not enabled? This might be allowing a larger error between your desired temp and actual to try and minimize energy use by the HVAC system.
Have you used the app on your phone to see what it reports as the interior temperature when you are seeing the large 8-9 degF delta in set point and actual temperature? It the phone is suggesting that interior temperature is much colder than what you are able to measure with an independent device, this would tend to support hypothesis that somehow the sensor is not tracking well.
I recall there is an ambient light sensor on the dash. I don't know this for absolute fact, but many vehicles will also use that as an input to HVAC auto controls, both in terms of which vents to bias airflow but also potentially fan speed. If this sensor is getting shaded so it's not sensing the true level of solar gain, this could also be messing up fan speed auto selection. Have you recently done something like tinted the windshield or maybe started placing a cap on the dash which could be covering or shielding this sensor?