With respect to the previous reviewer, Paranormal Entity 3 *is* a terrible film, in my opinion.
For what you're asked to believe is footage shot in the 70s, the film quality and colour saturation are far from authentic, undermining the whole premise. The aspect ratio, hazy after-effect and 70s shirt worn by the American film-maker do little to improve this. Personally, this was a major quibble.
And then there's the almost comical performance of the German doctor...
The series is linked by title alone and the stories bear no relation other than a paranormal theme and found-footage format. The first was pretty good, the second was passable... but the third? Terrible.