Fueling station assignments don't work across zone boundaries

I have a fueling station assigned to "export" to an excavator assigned to a mining tower in a nearby zone. The fuel-carrying vehicle refuses to travel to the excavator, so the excavator keeps traveling back to the fueling station (because it's the nearest station even though it is in a different zone). It took me a while to puzzle out what was going on because it was so weird to see the excavator travel to a fueling station with an idle fueling truck sitting right there.

Can you share the save?

Sorry, I should have realized you'd ask for a save, but I played the game all night and that autosave is gone.

I captured a save tonight of an issue that might be related with fueling stations. This save is looking at two excavators that are sitting there with no fuel. The mining tower they are attached to is served by a nearby fueling station which is full and has idle refueler vehicles just sitting there rather than fueling the excavators.

After further testing, I can say that this particular lack of refueling in this save is not a zoning issue, but instead is an issue with the trucks failing to route around a closed train crossing gate.

Not sure about the real cause but they move as soon as you turn on the difficulty setting "Stops working" for vehicles out of fuel.