Confirmed. Whatever you do in this game from that point on, whenever any player plays a Cultist, the game becomes stuck, the Cultist doesn't event start to draw 2 cards.
This is pure speculation, but I assume the fact that both players had chosen Caravan Guard for their Inheritance token plays a role here. That would explain that the game checks if there is a Reaction possible before the Cultist can do anything. But at the time when the game freezes, the oppoenent did neither have a Caravan Guard nor an Estate in hand. The strange thing is that Dwedit could play Cultist without problems on two turns before, when the opponent already had inherited their Estates.