Continuity mistake: In many interior places in the mansion heavy wind, rain or thunder/lightning can he heard on a continuous loop however when the player ventures to exterior locations in the mansion there is dead silence (to a point were only crickets can often be heard). This only applies to the 2002 RE remake to my knowledge.
Other mistake: The main character somehow finds Richard Aiken in a corridor that is locked with the armour key. The key is at the other end of the mansion so how did he get into the corridor without breaking the door down?