The AI is behaving strangely; the map was created in the Erathia version, and I replaced it with The Shadow of Death in the editor.
Perhaps that's the reason; a strong hero sits in the castle, while a much weaker hero stands near the castle.
They stand there for a month, and neither of them moves; the hero in the castle constantly buys an army and becomes even stronger, but he waits.
Also, there's a castle on an island, fully built; a hero comes by water, captures it, and stands at the edge of the water – he's my ally, and he has 0 mana.
He stood there for about 10 days, his mana recovered, and he summoned a ship, even though he could have entered the castle and spent the night there.