During the pool party, one teenager attempts to talk Freddy down, only to be slashed by Freddy and thrown towards a fire. When he is thrown towards the fire, there is no injury or damage to his clothes where Freddy slashed him.
When Jesse and Grady are fighting with each on the school baseball field and coach Schnider starts to walk over, in the background you can see the guy wearing the baseball mitt behind the coach. In the next shot you can see him encouraging Jesse and Grady to keep fighting with each other.
When Jesse's sister shows him the "Fu Man Fingers" they jump from her left hand to her right between shots. Also the cereal box she pulled the Fu Man Fingers out of, the box was on the table before she pulled them out. In the next shot the box is in her hand, then she pulls the Fu Man Fingers out.
When the coach is getting bombarded by basketballs and volleyballs one of the balls flies out, smacks him in the head and then bounces on the floor. At one point it is a volleyball and at another point it is a basketball.
When the first basketball launches at the coach after the rack has moved round, it is orange. When it strikes the coach on the head it is white, and then when it hits the ground it is orange but a different ball from the first ball that was launched.
The fictional location for the Nightmare on Elm Street franchises was Springwood, Ohio. Throughout the film Palm Trees are visible in the background which cannot be grown in Ohio climate and the bus in the opening scene drives through the desert, which is not part of Ohio's geography.
When Freddy Kruger jumps through a glass door and disappears mid jump. At the point he vanishes, so do several pieces of the doors debris. Clearly there were two takes, one with Freddy jumping, one without and they simply faded between them. This is very noticeable if you look at the door pieces at the top left of frame.
When Freddy attacks the kids at Lisa's pool party, he kills the first kid by slashing him diagonally across the right side of his face and neck. When the kid drops to the floor, the wounds are vertical and on the left side of his face.