Crash in the fifth mission of the third campaign in Heroes of Might and Magic V.

HOMM 5 v1.6 gold edition, licensed version
Markel is escorting Frida, but she doesn't reach Mythgard.
The game keeps crashing.
I started a new game.
I reinstalled Heroes.
It didn't help.
What should I do?

I found the problem myself.
You can't send Isabel to the Sanctuary.