Other mistake: When the clock strikes 8 o clock, the 11 (XI) on the clock reads 12 (XII) in roman numerals. This is just in-between the scene with the mice making Cinderella's ball dress and the scene where the carriage arrives at the home to pick the stepmother and stepsisters up for the ball. (00:36:50)
Other mistake: At the beginning of the movie, where Cindy opens the drapes outside of her stepsisters' bedrooms, you can see a slight stutter in her walk just as she reaches for the drapes. Looks like a camera mistake - the cels were out of sequence there.