Visible crew/equipment: Near the end when Diane is reaching for the kids and trying to get them out to the hallway, a film light is blatantly visible behind her. Also during the same scene the shadow of a fan can be seen in the hallway.
Continuity mistake: When the parapsychologists are attempting to record Carol Anne through the TV set, Ryan's hands are by his headphones, but the next shot shows him move his hands to his headphones again.
Continuity mistake: When Steve Freeling is in the living room with the Ghostbusters, he has a cigarette behind his ear. In another shot seconds later it disappears then reappears again.
Factual error: Robbie is grabbed by the big, gnarly tree outside his bedroom window during a severe thunderstorm, and Steve rushes outside to save the boy as a full-blown tornado passes overhead. The tornado sucks up the tree (which certainly weighs several tons); yet, completely defying physics, Steve and Robbie remain unaffected by the powerful updraft, even though the two are directly beneath the tornado vortex.
Continuity mistake: When the big throat is menacing the kids, Carol Anne's position swaps from being left or right to Robbie randomly between shots.
Continuity mistake: When the ghostbusters team goes upstairs with Steve for the first time, Ryan takes his bag off twice.
Continuity mistake: When Robbie is trapped by the tree and Carol Ann is about to be abducted, his bed cover keeps changing back and forth from messy to perfectly folded.
Continuity mistake: In the pool, Diane is surrounded by at least 4 bodies floating together; however, when she grabs the hose to climb up, half a second later, the overview of the pool shows just 2 bodies quite a distance each away from each other. In the next close-up, the 4 bodies reappear.
Continuity mistake: When Robbie covers the clown, the Chewbacca print on the jacket keeps changing in every shot.
Continuity mistake: Wen the tree grabs Robbie the toy by the window swaps from facing right to left back and forth.
Continuity mistake: After Robbie's mom kisses him goodnight, the helmet behind changes positions.
Continuity mistake: From the outside, Robbie watches the tree and walks backwards to his bed, made and with a green cover on. When the angle changes, the sheets are different and the bed is unmade.
Continuity mistake: The first night Robbie is watching the tree there are three Star Wars toys by the window. From the opposite angle, the amount and distance between each other is totally different.
Continuity mistake: While the neighbour's TV swaps from playing the football game to Mr. Rogers, the guy in green on the background lowers the phone. A frame later from a different angle his hand is up and he is repeating the previous movement.
Continuity mistake: After Dianne says "Stay away from the light" a scientist is standing behind a woman saying there might be walkie-talkies in the home. A frame later he is standing in front of her.
Revealing mistake: When the investigators open the kids' bedroom, some of the flying stuff becomes transparent or very light coloured due to the matte effect.
Audio problem: When CarolAnn slides across the floor, she comments on how it feels on her butt, but her mouth doesn't move.
Revealing mistake: When the TV is turned off and Diane insists it's left on, the picture rolls and color bars are visible before the picture stabilises again. The 'static' is a video signal being fed to the TV, not true static.
Continuity mistake: During the big-throat scene, Carol Anne's feet alternate between rapid up and down movement, still or just slightly up and down.
Continuity mistake: When Steve's high on pot and tells Diane he loves her, he has his hand raised. A frame later it's down by the blanket.
Answer: It seems that the majority of the activity was focusing in on the Freeling house exclusively. It's not fully explained why they were the only house affected, but there are a number of possibilities. Possibly because it's where the highest concentration of spirits were at unrest. Possibly because it could be inferred that the Freelings moved in first given Steven was involved with the company that built the community, and thus they became the first targets. And possibly because they were trying to get to Carol-Anne since she was an easy target.
Also, it is mentioned in the movie that Carol Anne was actually born in the house. That likely caused everything to focus on her.
It was not meant that Carol Anne was literally born inside the house, just while the family was living there. It was just a casual colloquial expression Steven's boss made.
raywest ★