Factual errors: When Irena is alarmed by the woman in the restaurant, she makes the sign of the cross left-to-right, as a Western Catholic would. However, as a Serb, she would more likely have made it right-to-left, as Orthodox and Eastern Catholics do. And if she was Orthodox, she would join three fingers (thumb, index and middle finger) to make the sign of the cross, not use the whole hand.
Factual errors: There was not a King John of Serbia who defeated the Mamelukes. None of the lists of Kings/Princes of Serbia include a King John. The closest historical personage was the Holy Martyr John Vladimir [St. Jovan Vladimir], killed by Tsar Vladimir in 1015 AD.