Storage not exporting with trucks assigned

I have had trouble getting some storage emptied when there's trucks assigned. The trucks just sit there, and do not do anything - even if there is an assigned export target. It is frustrating.
It could be helpful they'd alert with feedback if there's something wrong - and explain what they what they would need to function. That would be helpful.

I am able to eventually get things emptied through priorities. But it's logical that if there's a truck assigned they would export things.

Hi, can you show pictures of the U.I of both the storages AND the export target, or the expected target?

Then someone should be able to identify exactly what the misconfiguration is.