https://forum.paradoxplaza.com/forum/threads/im-export-bug-hints-symptoms-and-causes-all-resource-management-in-the-game-is-a-deception.1604434/page-4#post-29216506
Hi everyone. I just wanted to pop in and shed some light on this situation as resource management in Cities: Skylines II is, unfortunately, affected by a few bugs at the moment. We are aware of this and currently investigating these issues:
City services only trade with outside connections, even when storage companies in your city have the resources they need. They should of course be able to purchase the resources your city produces locally.
Harbors are mainly trading with your city’s storage companies, not other zoned buildings or city services. As you would expect, they should be able to trade with all zoned buildings and services, allowing your city to import and export through them.
We’re investigating reports that indicate the cargo terminal is affected by the same or an issue similar to the harbors.
It’s also worth noting that transportation distance affects costs. We expect that your businesses will prefer the closest storage facilities over a further away harbor/cargo terminal, however, that does not explain the reports we’re seeing.