Panzer Corps 2

Panzer Corps 2

PanzerCorp1-Grandcampaign
Leningrad 41 Suicide.
Playing Leningrad 41 and artillery that is supposed to be placed in 7 different places commits suicide in Novogorod. They appear on the eastern bridge and are surrounded immediately. I can't find any way to save them as they can't be moved. At best I've managed to save 4. Am I doing something wrong or has something gone wrong with the program?
Are there really only 18 rounds in total where these artillery pieces appear in round 4?