Revealing mistakes: During the scene where the angry- and invisible- Kitty Carroll is undressing in front of a startled Mr. Growley in his office, her black velvet clad arms (the actress was dressed in black velvet and shot against a black background as part of the invisibility special effects process) are distinctly visible when they cross in front of her legs and torso.
Continuity: At the lodge, the invisible Kitty puts on stockings so Dick can "see" her but moments later when she faints she's completely undressed again.
Continuity: When the butler trips down the stairs he throws the tray twice.