At one point, Javert and his officers wade through the sewers up to their waists in raw sewage. when they emerge, their light-coloured trousers have barely a stain on them, and are essentially clean.
The prison where Valjean is sentenced is identified as Toulon. It is depicted as a fortress used as a mill. The actual Toulon prison was a dockyard.
Valjean is shown being branded with his prisoner number, 24601. A number of prisoners are shown branded in succession but the men doing the branding are never shown altering the brand. Thus, all prisoners being sentenced that day would have been given the same prisoner number. In actuality, prisoners of the time were simply branded with a mark showing them to be convicts, not their individual prisoner numbers.
Apart from a single shot of a heated branding iron, none of the supposedly "hot" metal used in imprisoning Valjean and his fellow convicts (collar bolts, other shots of the branding iron) shows the metal glowing, steaming, or giving off any other signs of being heated.
The story is set entirely in late 18th/early 19th century France, yet the characters speak with a mixture of French, English, and American accents. Even accounting for them all speaking English via the "translation convention," there should still be some consistency regarding the accents.
When Valjean is rescuing the prisoner dangling over the wall, both men are clearly being held up by safety equipment.
When Monsieur Thénardier first approaches the conversing Valjean and Madame Thénardier, she is heard speaking but her lips are not moving.
The young Cosette has clearly been overdubbed with the voice of an adult voice actor.
The police prefect in Paris that Javert speaks with after Valjean's escape pronounces the name Thénardier with a "th" sound at the beginning. The name, pronounced correctly elsewhere in the film, begins with a "t" sound.