Active grille shutter issue

[Rapid Red Rocket]

While idling after my Explorer has already been warmed up I noticed a constant clicking for a 3 seconds at 20 seconds intervals. I realized it was the grille shutters constantly opening and closing. I got out and saw them do this over and over again and I thought "just pick a position already." They weren't adjusting to any apparent necessary changes to the engine or outside air temperature. The vehicle wasn't even moving. Then I decided to just drive around the block and see if that would change anything. While driving, from inside the vehicle I could still hear the shutters constantly clicking and changing positions for 3 seconds at 20 second intervals. The vehicle drives fine and doesn't seem to want to overheat or anything but I'd like to know what the deal is. I already know that when you first start the vehicle they'll probably turn closed to help warm up the engine and then open again when the engine temperature levels off. Then for aerodynamics if the vehicle reaches a certain speed then they'll close again. But let me know if anyone else can explain what mine are doing.