Continuity mistake: Vogler paints a target on Illya's shirt back and hunts him. The target remains constant through most of the chase, until a stunt double is brought in for a fight sequence. The double's target has a large "bite" taken out of the bull's eye. The bite goes away after the fight, and Illya's target is whole again.
Continuity mistake: Solo sneaks down an empty corridor and knocks out the only man guarding the lab door. When the camera angle reverses, there's a second unconscious (or dead) man on the floor behind him. Where'd that guy come from? Solo didn't encounter anyone before the door guard, and there were no bodies already on the floor when he entered the hall.
Continuity mistake: When Illya talks with Carl Voegler in the woods, Voegler rests his bow on the ground, gripping it with his right hand and his left arm resting on top. In the next shot, he's gripping the bow with his left hand and his right hand is instantly down by his side.