When truck starts air blows out vents and then switches to defrost on its own

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Truck air was stuck on vents. Had heard clicking sounds. Replaced blend door actuator on lower driver's side. Went through recalibration. Now when you start the truck the vents will turn on but then it changes to defrost and won't change from there until you restart the truck. Then it changes back to vents and right back to defrost on its own, no matter where it's set. Don't know what I should do next. Considered changing the control panel but didn't think that's the problem since everything else works on it.