Factual error: When Ian is checking his laptop and Nica is bound and gagged behind him, you can see her moving her feet a bit, even though she's supposed to be paralyzed.
Continuity mistake: When Nica smashes the car window, there's still a lot of glass around the frame. It all vanishes in the next shot.
Continuity mistake: The amount of blood on Nica's clothes changes repeatedly during the final half-hour of the film.
Other mistake: It makes no sense for Ian to have so much blood on his shirt after he grabs Nica and carries her down to the garage. She didn't have enough blood on her to coat his shirt.
Other mistake: This is hard to describe. When Nica finds Jill's dead body, you can see the side of her wheelchair and feet on the right side of the screen, and they've been laid over the top of the image in post-production. Their angle literally makes no sense. Her chair would have to be leaned 45 degrees to the side for the shot to be possible. Jill also wasn't close enough to the door where Nica is for the shot to be possible.
Continuity mistake: When Barb pulls the first few bits of skin off Chucky's face, it's very noticeable when they switch from one Chucky prop-head to the next. Suddenly, the stitching (especially on his lip) has much more detail, and some of the imperfections vanish.
Continuity mistake: When Barb notices the "loose skin" on Chucky's face, it just sort of appears between cuts. The implication was that it came loose over the film but up until that very shot, his face looked pristine.
Continuity mistake: When Barb puts Chucky down in the attic, when the rocking horse scares her, Chucky's face goes from being in the shadows to illuminated instantly between cuts.
Factual error: When Nica is pulling herself up the stairs while Barb is in the attic, at one point she calls for Alice. Right after this, you can see her subtly bend her right knee. She's supposed to be paralyzed, so this shouldn't happen. The next time it comes back to her, you can also subtly see her moving her feet and toes a little bit.
Deliberate mistake: When Barb is in the attic, she finds two pictures of sunflowers in front of her. It then cuts to the "opposite" angle of Barb, and those exact same two pictures are suddenly behind her. In fact, everything behind her is the same. It appears to be two slightly different shots from the exact same angle that they tried to "cheat" as being two different angles. (They almost get away with it because the second shot is wider, but once you notice the pictures, it's far too obvious.)
Continuity mistake: Barb turns the flashlight onto the child's wheelchair twice between cuts in the attic.
Continuity mistake: Right after Nica and Barg get into an argument over the doll, Nica's feet go from together to about 6" apart. The character is in a wheelchair and can't move her legs, so this makes no sense.
Continuity mistake: After Nica gets into an argument with Barb over the doll, Nica pulls out her phone and then slams it down into her lap. Immediately in the next shot, the phone vanishes.
Continuity mistake: When Chucky kicks the bucket over, not only can you see the water hit Jill's feet twice between cuts. And both times, the way it hits her feet is different, revealing it's two different takes. (The water is more forceful the first time, while the second it's a bit "softer.")
Visible crew/equipment: When Chucky kicks over the bucket to electrocute Jill, you can just barely see something small and white sticking out from underneath the bucket, which moves when the bucket tips over. It appears to be part of the mechanism that actually "kicks" it over.
Deliberate mistake: The video feed from Jill's laptop doesn't match the angle we see her laptop in. The image should be a weird, low-angle shot with lots of space above her head given her laptop is down on her lap, but the image we see is a pristine parallel shot. Additionally, the video footage is way too high quality for a 2013 laptop webcam. (Heck, it's too high quality for a 2024 laptop webcam.)
Continuity mistake: When Barb and Jill are flirting over a video call, the second time Barb tries to signal Jill that she thinks Alice is up, her hand gets much closer to the laptop between cuts. (In the first shot, it's up near her shoulder; in the second, it's right over the laptop keyboard.)
Continuity mistake: When Nica and Barb are talking after Alice gets Chucky back, there are several minor back-to-back continuity errors as it cuts between Nica's closeup and the side shot with both women. Nica's mouth goes from closed to open and back a few times. Nica's arms aren't folded, then it cuts to the side shot, then it cuts back and they're folded. (We would have seen her move to fold them in the side shot.) And the direction she's facing changes subtly at least once.
Continuity mistake: When Nica gets in the elevator to take Chucky up to Alice, when she closes the door, her right arm is suddenly fully extended to flip the switch between cuts.
Continuity mistake: When the nanny notices that the knife is missing, right before Barb starts kissing her, the knives on the rack change when it cuts back to a closeup. Noticeably, the butcher knife from the first shot has been replaced with a much smaller standard carving knife. One of the other knives has also rotated about 20 degrees.
Answer: It's not any problem and trouble in the film. Maybe it's just a reflection of light in the bed.