Smithers glitch?
I've had this. I think I just stored the control building. If that doesn't work, try storing Burns' Manor.
Forum Discussion
It's been a common problem. Smithers gets stuck in the control building, and sometimes it says there are two or three of him on a job in there, a problem I had to store the manor to fix. I've been keeping him away from the plant until there's a patch or something.
