Found a bug:
At the end of chapter 3 I had given a hero group the task to attack a camp. While they were on their way, I successfully completed the final fight for chapter 3. Following to chapter 4, some of the heroes of the attack group have retired.
In chapter 4 one of the heroes was on his way to attack the camp, despite his retirement. I can't abort the command and when it comes to attack the game breaks down while generating the playing field.