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Played through it again, but without logging, in 124 days (2037 - Cyclops).
The catapult doesn't appear if you don't control all the mines.
In the tavern of the Dwarven Castle, you might not find any heroes, and they won't appear until the end of the scenario. This forced me to replay. Lorenzo fled the battlefield from the turquoise enemy, and the heroes appeared in the tavern.
If you equip Bertrand with the King of Dwarves set before the battle, he becomes weak. He stops dispelling enchantments and almost always attacks with his bare hands.