This is "Invention" tech is trying to update graphics. But because it is happening during diplomacy screen, result is not so nice. No easy fix is possible in hex. With access to source code we can check that this happening during diplomacy and disable it in this case, but I'm not too sure if in this case game will update graphics correctly later. Maybe it will, because transition diplomacy => main game is pretty big and probably graphics is updated here every time. But I'm not sure.