Hey @LT586,
sorry for the late reply to your problem, I had to find out myself what's going wrong there.
It seems like there's an issue with Steam itself (Steam likes to mess up game data here and then). I would suggest reinstalling the game completely.
To do so, uninstall the game via Steam. Afterwards, go to the game installation folder (.../Steamapps/common) and delete the "Fernbus Simulator" folder completely. No worries, your user profile data is not affected. Then head back to Steam itself and install the game again.
Please let me know if this works out.
Thanks,
Chris