After the evasion of one musketeers his brother, coming from La Rochelle, wears glasses. The glasses are a 18th century model while the action is supposed to take place way sooner in 1627
The action is set in 1627. By the end of the first installment (d'Artagnan) attends the wedding of king's brother, Gaston d'Orléans, with duchess of Montpensier. It's inaccurate. Actually the wedding took place one year before in August of 1626, as a consequence of the failed Challais'Conspiracy. The Dutchess died in 1627 when the story is supposed to begin.
Many of the windows in the film have panes that are far too oversized for the 17th century. Glaziers of this era could not make large areas, so they used stained glass.