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.