When the wardrobe department tried to clean the lancers' uniforms after their tar pit scenes, they discovered that the dry cleaning fluids and tar combined to severely shrink the uniforms and the filming had to be rescheduled while new ones were made.
At approximately the 3/4 mark, during a chase scene where the soldiers are following Zorro, one of the soldiers swords comes loose from their scabbard and goes flying into the bushes as the whole group continues to ride on. It is likely that no one on set noticed at the time and even if the error were noticed in editing; a reshoot would have been costly.