Mark Smeaton is the last man brought before the executioner. Oddly, even though the executioner has chopped off several heads, his axe is completely bloodless when Smeaton is placed on the block. When the executioner raises his axe to swing, the blood has magically stained it again.
At George Boleyn's execution, the crowd is depicted as loudly booing and jeering, so that he can't be heard and cuts his speech short. In actuality, George Boleyn's lengthy scaffold speech (mostly to do with his belief in the Reformation) was recorded in full, so the crowd would have been relatively quiet and respectful.
Right after Brereton is executed, we can see the executioner swinging his ax a couple of times, like he would chop off several heads. But at one point (at the fist swing) we can actually see, that there is no one kneeling in front of him, he is just swinging the ax in the air but the audience is reacting like a head would have been chopped off.
When Queen Anne's alleged lovers were executed, after William Bereton and before Mark Smeaton was beheaded, the axe was shown to have fallen twice, making it six times. However, when the first one fell, you could see through the gap in the crowd there was actually no one on the block. Also, in actual fact, only five were executed that day, with only Francis Weston not shown on screen as he did not exist in the series.