Air comes from the wrong vents

So a week ago I went in to the auto shop to get my dashboard air vents checked out as no air was coming from them. Shop ended up fixing it, the part that was broken was called an air mode actuator. Took it home that night and the air mode selected was for the foot and dashboard vents. So air was coming out of the dashboard vents. But then I switched it to dashboard vents *only* and the air was coming out of the windshield vents. Switched to "feet" vents and then the air came out of the dashboard vents. So it seemed like maybe the shop just did something wrong and could get it fixed up real quick. Took it back the next day, and they told me they had taken the dash apart to check on the part they replaced and everything was working fine. Put it back together, and suddenly the air was coming out of the correct vents with respect to the air mode chosen. According to them, they didn't even do anything different it basically just spontaneously started working. So for a couple of days everything was fine, then this morning I had the dashboard vent *only* mode selected and the problem came back up--it would only blow from the windshield vent. So I'm wondering, is this something mechanical or technological? Is there something I can do to "reconfigure" so to speak these **** buttons and what vent they should activate? Is my only recourse to take it into a Chevy dealer as the shop suggested?