On a trade route that unloads from the warehouse, if the amount of cargo remaining in the warehouse is less than what will fill the fleet, the fleet does not load the cargo from the warehouse. The only way around this is to manually load the remaining goods or add more goods to the warehouse so the fleet becomes full. This is specifically a problem when you need or want specific amounts of cargo transported.

The suggestion is to correct this, so that the fleet continues to load any available (of the specified) cargo from the warehouse into the ships until the warehouse is empty, even if this results in a partial load on the fleet.