When Isabella is at the beach for the first time and encounters the boys, there are seven of them at first, and once she is out of the barrel, there are only six boys present.
When the Prince is thrown from his horse, the saddle lands in a fairly clear area. When he picks up his saddle, it is from a grassy area.
Joseph of Cupertino died on 18 September 1663, which means that the plot of this movie takes place in September of 1663. The fashions, however, are from the beginning of the 17th century; the ruff, for example, was no longer in fashion by 1663.
Near the ending, when Isabella encounters the flying Saints, the wires above them are visible for one to two seconds.