Welcome! This is the new clubhouse for discussing technical issues. Curious how you discovered us, since trailvoy attempts to censor any mention of the couple thousand "disloyal ones".
Anyway, it really takes a GM Tech II tool to take control of the HVAC control module and put each actuator through its paces. If you recently changed or discharged the battery, the lack of voltage to the control module memory forces each actuator through a recalibration process. That process is often stressful to older actuators and they get flaky or die.
Perhaps you've seen my main actuator location diagram:
There isn't much chance for actuators to interact unless the wiring has been chafed and shorting out at the back of the control module. Left and right temperature actuators are separate, but your issue sounds like confusion in the airflow mode actuator, that manages the airflow split between feet and center dashboard outlets. If you're in heat or AC mode, you can manually take control over the airflow mode and cycle it a few dozen times from feet to cehter dash. Ignore the defrost/windshield airflow because that's a separate actuator. If the actuator won't reliably move where you tell it to go, just swap it, is my recommendation. Only $33 on Amazon and you can check your own local parts stores.