When playing without sea attacks (just hit default s2 settings) indicator flags are not updated by hostile harbor buildings - this means your buildings are not occupied and you can not attack them.
Just found out that this depends on the order. If the harbor building is finished first, the flag is set correctly - but if the harbor is finished after the military building, the indicator flags are not updated.
When playing without sea attacks (just hit default s2 settings) indicator flags are not updated by hostile harbor buildings - this means your buildings are not occupied and you can not attack them.