In some scenes Rick has wet (50s style) hair and in other scenes he has dry hair.
When the tilt a whirl stops suddenly, the actors are obviously throwing themselves off the platform as opposed to it looking accidental.
When Janet gets bit by the stairwell buzzard, there is a flap in the back, revealing it's a puppet.
In some scenes, like Janet's death, there is stretching walls. These walls have tearing latex on them.
The ghostly footprints on the beach are a problem if the are supposed to be from 1959/60 since the Dr Martens Air-Wair sole was not introduced into the Uk until April 1960.