Not a bug but something CA needs to fix
I situated my army across a river bridge. Brutii, come, I am not afraid of your great numbers, I thought. But the devil gave me bad advice - why not also construct a fort in addition to river defence? So I did, smearing. As it appeared after turn button pressing, brutii cheerfully crossed the river and besieged my fortification. This is not logical, because if there werent fort they would have to storm the bridge. Who would make fort away from the river? Romans did not at their river borders, so would not any reasonable ruler