Just gotta keep paying attention to them dude. If it's when you transfer trucks from one patch to the other and they return home to Thier old refinery like a lost dog, what I tend to do is command stop then click the new ore field
"I love the smell of JuiceBoxes in the morning"
LT. COL. Bill Kilgore
Apocalypse Now
Another way I find if you're transitioning them is to tell the truck to deposit in the new refinery (even after depositing in the old one and is empty) followed by the new patch of ore you want it to go after. That way locking it to the new refinery.