Vehicles Heading Towards Airport Exit -- Why?

This image shows a Fuel Truck and Pusher exiting the airport. They are on a Service Road, driving towards a Vehicle Checkpoint. Upon arriving at the Checkpoint, they immediately reversed course to drive back to the Vehicle Depot.

These two vehicles were blocking each other at a medium stand. I saved the game. Reloaded. This this situation happened.

Question: why did they do this? Looks like a bug.

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If you add a cross road, like a T, do they turn more early?