In the scene where the young Earl of Oxford has dinner with Queen Elizabeth, he mentions that the Italian actors are called Commedia Dell' Arte. The name Commedia Dell' Arte was not coined until the 18th century by Italian playwright and librettist Carlo Goldoni.
The playwrights in the movie are all astonished that Romeo and Juliet is written in verse, specifically iambic pentameter. In fact, English drama had been written in verse for hundreds of years, and mostly in iambic pentameter for about the previous 25 years. Prose drama, not poetry, was the innovation.
When Ben Jonson first arrives at the home of the Earl of Oxford after being released from prison the Earl is shown cutting, holding, smelling, and then referring to a white and red rose as "The Tudor Rose". "The Tudor Rose" is actually a heraldic emblem of England that is a combination of the white rose and the red rose of the House of York and the House of Lancaster, respectively. It is not, nor has it ever actually been, the actual bloom of a rose bush.
The music at Oxford's wedding in 1571 is Mozart's Requiem, composed in 1791. However, at the time of protestant Elizabeth I, music was not performed at weddings at all. Furthermore, Mozart's requiem is reserved for solemn occasions such as funerals and would never be played at a wedding, protestant or otherwise. Regardless of these facts, it is simply part of the movie's soundtrack, and it is not implied that the musicians in the film are playing it.
(at around 1h 50 mins) When Jonson is thrown out of The Globe, the Earl of Oxford's man's image is printed backward with the Earl's Crest reversed and on the right breast rather than the left breast and the buttons on the suit backward, because the image was flopped in editing.