Critical problem in siege battles

[TheChronoG]

When an enemy fleet attacks one of your coastal settlements and gets reinforced from an army on land, if you destroy the fleet or make so that they can't disembark their men into the city, the battle is stuck. You have to wait until the time runs out because the land army doesn't admit defeat, but it can't enter the city as it has no siege machines. Syracuse and Rome keep doing this to me in my Carthage campaign, it's unplayable.

[Tazgrent]

You don't need siege machines to enter a city; soldiers can torch the gates.

[CatoTheYounger]

But he is saying the AI isn't doing that.