Mining Assigment Question (noob)

I got all of my 10 M Miners assigned to my Refinery Station to supply the Ore. The station sits in Hatikvah's Choice III but the Miners go to Heretic's End to mine the ore when I assign them to the station. Is there actually a reason for this or is it just bugged? The way that they have to travel is way longer than if they just mine in Hatikvah's Choice III, why arent they doing it?