Mission... Highly Improbable - S5-E24
Continuity mistake: When Steed begins cutting Mrs. Peel's bonds, they're black straps. When he finishes sawing through them, however, they've turned into ropes. (00:42:00)
Too Many Christmas Trees - S4-E13
Continuity mistake: When Steed and Emma are driving to the estate, the car's windscreen keeps disappearing. It's there in full shots, gone in close-ups, and reappears again every time we cut back to a long shot. (00:10:30)