I just attack Pennsylvania with a french group of irregulars.
All defenders have been eliminated but the deposit and the fort structure have not been destroyed.
I think the problem may be the presence of enemy naval units.
My units are continuing to besiege the city when there is no ground enemy forces.
The rigth had been the destruction of the structures and the boats had left the city.

Attached files saved if interested check them.
Thanks and best regards.