Unassigned and unused trucks don't deliver iron requested at the shipyard

In the picture you can see there is an idle truck that doesnt deliver iron to the shipyard even though i have enough iron

"Brak zleceń" means "No tasks" in Polish

🤔 Are you sure that this isn't because you're using
export routes on that storage structure & therefore
blocking anything else besides those structures
from requesting the stored goods?

If that's the case, then this is almost
certainly intentional behavior.

export routes will block all other exports, unlike for imports there isn't an option to override that behaviour (maybe there should be but that also defeats the whole point of routes), next best option is to assign another storage route that also connects to another unrouted storage for general purpose, or simply have a secondary storage alongside the main one, you can use the belt export sliders and balancers to tune priorities