The cake on Mrs. Dubrow's gown changes between shots.
When Dunston goes into the spa and takes the cucumber off of the woman's face, it remains missing. But when Mr. Grant comes in, the cucumber is back on her face.
During the Royal Suite scene, the shirt under Kyle's overalls changes. Even if one assumed that Kyle "packed an extra shirt" when they brought Dunston to the suite, the shirt change would still be an editing error as the shirt changes twice AFTER Kyle takes a bath.
After kidnapping Kyle, when Lord Rutledge gags him with the white masking tape, the strip he has ripped off is long enough to reach Kyle's ears when applied. When Dunston comes to free Kyle, the strip of tape across his mouth is not nearly as long and also has a cleaner cut on the ends.
The bandage on Dunston's hand.
When Kyle sets the video camera in the bathroom and Dunston appears and shoves his head down the toilet, the toilet wobbles, suggesting that it may not be a real toilet.
When Lionel gets his glasses off the cucumber woman's chest he is holding the end of them. When the camera changes he is not touching the glasses at all. When it goes back to the first camera he is touching them again.