Hi
this looks a bit like the bug that sometimes appeared in 1.03 (ie the bug that Narwhal reported here). I have attached the saves for two turns. Battle Turn#1 has a siege of Stettin with my Prussians gaiing a second breach and assaulting. First battle is as expected but then that last artillery unit is immune and triggers battle round after battle round but the fort doesn't fall.
[ATTACH]21268[/ATTACH][ATTACH]21269[/ATTACH]
Just as a test I reran the turn and almost exactly the same - I think the second run the last Russian unit was only 17 men but it still replenished every combat round
ta