I'm in a mine with 12 dirt haulers.
Haulers are Krath dynasty owned
Mine is krath owned
In the mining process it tells me
=Only able to find 0 available workers (you asked for: 5). Workers in your party are not counted.
=An error occurred: Mine must have at least one Dirt Hauler assigned.
I tried all 12 haulers,5 haulers, and even just one.
Mine is powered.also, not that this matters,but the npc's won't even join party for some reason.
I found a loophole. If I buy just one new NPC, and put only him to work, he automatically adds the others with him. Confirmed by percentages on inventory of NPC's.
Of course, this don't fix the original problem.