November 2017
Just had the same problem. I’m playing in single player, so the fix for me was just to go into the regional map, find out where all the trucks were piling up, load up that city and voila, it’s fixed. If you don’t own the city, I don’t know if it can be fixed, other than asking the person to fix it.
May 2022
The year 2022 checking in. Bug still exists! Amazing.