When Pepys is telling Kynaston to play a man's role, Kynaston's lips are out of sync with his speech in some shots.
When Kynaston says, "I blame you for my death," he looks up at Maria, but in the next shot his head is back down.
The word "fan" (short for "fanatic"), meaning an enthusiastic admirer, was not used in this sense until the late 18th century.
"Sex" is used by characters as shorthand for sexual intercourse, a meaning the word didn't have until the 20th century.
The "naturalistic" acting, as Ned and Maria perform in the later part of the movie, wasn't done until the 19th century. The "series of poses" acting done in the early scenes was the norm for some time after the film is set.