When Mrs. Bennet is seen steaming open the letter to Jane from Caroline Bingley, the envelope is a modern day gummed envelope fit for stationery letters. The year the film takes place is 1815, letters would have been folded in and sealed with a wax seal.
Gummed envelopes would not be invented for another 100 years; therefore it should have been impossible for Mrs. Bennett to steam open a letter that had been sealed with a wax seals.
Early in the movie, Mr. Bennet is sitting in his study smoking a pipe when Mrs. Bennet and the daughters return from the village. In anticipation of their arrival, Mr. Bennet puts his pipe into the rack with other pipes. Yet, when Mrs. Bennet enters the room, he is seen smoking the pipe.
When their cousin, Collins, is expected to dinner, the butler comes in to light the candles. The mother asks the butler about Collins and when the camera cuts back to the butler, all the candles are lit.
At the dance in Meryton, George Wickham remarks "Ah, polka mazurka!" However the dance music that is playing and continues to play is in triple time, typical of a waltz. The polka is invariably in 2-4 time.
In the first "Ball" scene, right after Elizabeth says to Jane, "My goodness, he does have an air about him.", the camera pans onto the dancers. If you watch the 4th girl from the camera (17: 50 minutes), when the women curtsy, #4 almost tips over and shoots a worried glance toward the director.