I had an importer that wasn’t being used hardly at all, because it was across the plant. At the same time, I was running short on glass and steel on the other side, as those importers were overwhelmed.
I tried putting a few steel and glass stockpiles near the idle importer. And the flood gates opened. The importer started feeding glass and steel to the line that goes across the factory to where it is needed. The manufacturers were getting the stuff.
The moral of the story is even if the resource is not needed right there, once it enters the building, it may not make a difference. The need to fill the stockpile may be enough get things moving.