Other mistake: When one of the Christians is being crucified and burnt, we can see that just after the man's "death" the body is substituted by a plastic doll covered in red paint.
Other mistake: The day after informing Lady Barbara that he was married, Hornblower, in a rush to get home, orders the t'gallants set. But the ship, as shown in the prior scene, already has them set.
Other mistake: When Clift stops rowing, you can still see apparent boat movement in the backdrop film of the lake, more than you could attribute to forward momentum.
Other mistake: Lock Martin is not wearing his Gort glove on his right hand in the first frame of him carrying Patrica Neal.
Other mistake: In all of its appearances, the British flag (also known as the Union Flag and the flag of the United Kingdom) is wrong. The flag's X-shaped red Cross of Saint Patrick is shown as (a) wide, and (b) centered on its white background, whereas on the actual flag, it is (a) thin, and (b) not centered on its white background, but rather off-center in a counter-clockwise direction.