Continuity mistake: The Fleshlumpeater narrowly tracks Sophie, who hides in the snozzcumber on the table. He almost eats her after being persuaded by the BFG to try it. Right before he bites into it it changes directions.
Continuity mistake: Right at the start of the film when Sophie comes back into the dormitory at 3:00am, she leaves the door open. Then when she is in bed reading and hears someone (matron) coming, you can hear the door opening and then see it being thrown open as matron enters, as though it had been closed.
Continuity mistake: Sophie is sitting on the Queen's window seat and the curtains are open, but after the queen wakes and remembers that in the dream a little girl was sitting on the window ledge, she tells Mary to draw the curtains.
Continuity mistake: Sophie's glasses start out as reading glasses, but later she wears them all of the time.