Final campaign - "Too Bright for Darkness [Campaign 7 - Mission 2]"

An insurmountable problem has arisen: I went down, captured one Fortress, and now I can't fight with the orange heroes – the game crashes. It crashes in a standard way, as soon as my troops want to act. Sometimes I can act with the snohodtsy, the rest of the troops do something – and then it crashes. Has anyone else experienced this?