Designate truck cargo as "Unsorted cargo" (i.e. dirt, rock, ore)

Since recent patch some of the trucks get stuck, couldn't figure out why. For example, truck was sitting next to Sorting plant and wouldn't dump. I THINK it was because despite being all ore (20 units) it wasn't sorted yet, so it treated the cargo differently.

Your statement confuses me. If the truck's load is a single resource there is no reason to sort it. If you want to dump the resource in a sorter configured to sort that resource regardless of whether it is mixed in the load or not then there is already a checkbox for that.