As Sherlock reaches into the coffin to lift Lady Carfax, Watson is seen running toward him. The editing them makes it looks like Watson comes to assist, but then Sherlock is seen to repeat the identical lift of Lady Carfax.
In the opening scene, as Holmes holds Watson's letter, it is blank at the top of the page. A moment later as the letter is sitting on the table and Holmes places figurines on it, the hotel's letterhead is imprinted on the top of the page.
The "corpse" can be seen to breathe and swallow.