I had a car project done all the way to the last page before signing off, had the factories all set up and then decided to delete the project before signing it off because it just wasn’t profitable. But the factory remained and now there’s a factory listed that I can’t use. The setup icon for it is blinking as if it’s waiting to be set up but it’s also greyed out and I couldn’t choose the factory for another car project.
Thanks for pointing that out! In case you remember how you got into that situation it would be very useful to know in order to fix the issue 
we’ll look into it.
I made a test company and tried this again.
First I made the first car normally so that the starting factory gets used.
Then I started a new car project, setting everything up all the way to the sign off page, but did not sign it off.
Instead I deleted the project.
At this point when I go to the Factory Manager, I have the starter factory and an extra factory from the new project even if the project wasn’t signed off.
If I press the setup button for it, I get this
And if I agree, I go to the factory setup for that factory and when I exit that, I now have the ghost factory.
Apparently simply going to the factory manager to buy a new factory and then deciding not to buy it after all and backing out of the factory buying menu does it too.
