Glitch with the passage through the gates of Chalassa on map 3 for the League of Shadows. (Might and Magic: Heroes 7)

Who faced this problem ??? There, in one of the tasks you need to go through the gates to get into the library, I kill the guards, I go to the dragon's source and run to the gates, but they do not open, in general, this is such a situevina, if anyone knows how fix or write something else, thanks in advance !!!