From the frying pan into the fire.

To be more precise, the crash occurred after the cutscene following the victory, but there was no save before the battle. However, I killed him outside the castle without any crashes (hero difficulty), so the mission is completed.

Added 5 minutes later
And yes, thank you for another impressive piece of work.

Added 3 minutes later
I downloaded the map yesterday or the day before, and it seems to be the updated version.