Continuity: While the Rutles are on stage playing "Between Us", Stig's guitar changes from an acoustic to an electric, and then quickly changes back.
Crew or equipment visible: As the Rutles get off the Bognor Express train, a cameraman with a 1970s movie camera is seen following the Rutles out. This recognized as a mistake by Eric Idle on the DVD Director's commentary, where Idle also identifies the cameraman as Gary Weis (co-director and chief cinematographer).
Plot holes: Late in the "documentary," the Rutles' tea-drinking is treated as a scandal (parodying the Beatles' marijuana use). But in an earlier scene, there doesn't seem to be anything unremarkable about it, as the band members play with a teapot in their hotel room while on camera.
Anachronisms: In one scene the Pre-Fab Four are in front of a wall with some graffiti in it. The words spell the name of a group that didn't form until 1972: Be Bop Deluxe.
Errors made by characters (possibly deliberate errors by the filmmakers): When the narrator tries to describe the actual sound of singing "SERGEANT RUTTERS ONLY DARTS CLUB BAND" backwards, the on-screen title displays "DNAB BULC STRAD YLNO SRETTUR TNAEGRES" which are all the letters in reverse order, but he says "DNAB BULC YLNO SRETTUR TNAEGRES" failing to pronounce STRAD, or DARTS backwards.
Revealing mistakes: When the Rutles toast with their cups of tea and drink, it becomes obvious that Stig's cup is actually empty.
Anachronisms: In one of the movie scenes where The Rutles descend an outdoor fire exit/staircase, there is a 1970s VW Rabbit parked near the base of the stairs. The scene supposedly took place in the mid-1960s.