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.
Not sure if Sin fixed it, but the dirt haulers used to have to be owned by the faction doing the mining. So try making the NPCs over to the medical faction doing the farming, and see if that helps.
They definitely don't need to be owned by the faction who is manager of the mine, just assigned. It's been like that for a while too. At least we're all more informed now.
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.
Did you make a bug report? Since its fairly likely that it is nothing we can fix, only a coder can take a look and they are unlikely to look here for bugs.