red exclamation point

Hello there, I'm re-assign a unique building from a civilization (Palgum from Babylon) to another civ (Germany). Everything works, except for the visuals. I got a red exclamation mark on my map. This should be easy, right? I've spent 3h trying to read some threads debating similar subjects...

Hi, When I reload a save game with my custom Library replacement the base doesn't show correctly: I can find no log entry that seems to refer to this error. Sadly it works fine when I use FireTuner to add the building and when I build the building in the normal manner – It only shows up...