Lilith, I know there is a new interface for mines and I'm assuming farms (which are a mine) are the same. I haven't seen it myself and there could be a bug, but that's what's going on.
Apparently it's supposed to automatically detect and add the dirt haulers present (I realize this is a farm). The rules under Bacta Creation outline who the farm needs to be assigned to and I presume the NPCs will need to be the same.
Yes I am using a medical faction. No they were not in my party. They are inside the Command room. I did it before and it worked perfectly fine. The new interface and code should have been tested more it seems.