Horror movies, by their very nature, require viewers to suspend their disbelief, as they are routinely inexplicable. After all, would a couple of teens really wander into an abandoned warehouse in the middle of the night only to split up when they first hear some frightening noises?
Of course, they wouldn't, but the average victim in a horror movie must exist in an alternate reality where horror movies aren't a thing. Still, suspending our disbelief only covers so much, as some scenes require more than a simple suspension of disbelief; some scenes either don't make sense, or they defy explanation.
That's not to say the scenes didn't work for the movies they were in, nor does it mean the movie itself wasn't extraordinary. All it truly means is that a rewatch of a film might make a viewer do a double-take after seeing a scene or moment in a horror movie that is never fully explained.
Once the credits roll, that's it, so if the scene in question remains unexplained, it tends to stick with the viewer. Did what happen really happen, or was it something unintentional on the part of the filmmakers? Either answer may be true in these eight films that contained some truly unexplainable moments.