Factual error: While handling the ignition coil cable to the distributor cap, Joe Pesci tells De Niro that the timing chain needs adjustment in his truck. A truck of that year with an inline Chevy motor would not have a timing chain at all, instead this truck would be equipped with a direct drive timing gear. Even if it had a timing chain, it would be behind the water pump and a cover. It would have been a several hour job to replace, not possible to adjust it.
Visible crew/equipment: At the beginning of the film when being rescued from the quicksand you can see someone's legs and hand behind the horse, holding it. (00:10:00 - 00:11:00)
Continuity mistake: When Elton and John Reid are kissing in the cupboard John's hand keeps changing between shots. John's hand rolls down Elton's chest, then the next shot it's on Elton's cheek, the next shot he takes his hand away, then the next shot his hand is by Elton's mouth and Elton pretends to bite John's thumb.
Continuity mistake: After Mick Mars has Nikki and Tommy kick the guy out with the guitar at his audition, the guy leaves and cries through the door. Nikki is standing by the door and looking nearly straight forward as the guy leaves, but then the camera changes angles and suddenly he's looking more to the side towards the door. Also his arms are a little higher up holding his guitar.
Factual error: In 1915 Tolkien was commissioned as a Second Lieutenant with the Lancashire Fusiliers. He (plus various other officers) is constantly shown in the film wearing bright metal cap badge, collar badges and shoulder titles on his Service Dress tunic and greatcoat. However, in the Lancashire Fusiliers officers did not wear shoulder titles on their SD tunics/greatcoats, and their cap/collar badges would have been in a darkened bronze finish, not bright metal (which was for Other Ranks and NCO's).
Continuity mistake: On the subway, behind Mr. Rogers, the sign showing the train's destination changes.