Continuity mistake: When Andy is grappling with the "buzz-cut" Chucky and trying to rip his clothes off, at one point the camera cuts from a medium shot to a closeup as he rips Chucky's overalls down. In the medium shot, Chucky's left arm is reaching for Andy's wrist, but isn't holding it. But in the closeup, suddenly Chucky is grasping Andy's wrist.
Continuity mistake: Dr. Foley burns and melts the Chucky doll on his right hand with a lighter but when it cuts to a wide shot, Chucky's hand is completely fine.
Continuity mistake: When Nica-Chucky stomps Foley's head in, you can see a ton of brain matter coming out in the wide shots. But in the final closeup, there's only one or two little pieces.
Continuity mistake: When the security guard looks in the window of Tiffany's car, there's no snow behind him, even though it's falling in every other shot.
Continuity mistake: When Carlos dies, when his head falls over, the blood on his face changes between cuts.
Continuity mistake: Malcolm goes from watching Madeline's body being taken away to looking at Dr. Foley between cuts when he makes a quip about how Foley must be having a "bad day."
Continuity mistake: When Nurse Ashley takes the shoe from Madeline, Madeline's hands change positions repeatedly between cuts.
Continuity mistake: When Dr. Foley pours himself a drink while Nica is hypnotized, the bottle cap goes from right in front of him to about a foot to his left instantly between cuts. It then reappears on the bottle a few shots later despite him having not put it back on.
Continuity mistake: When Foley turns to Nica with the needle, in the shots over his shoulder, he's holding it below shoulder level (to the point it's not visible on camera), while the shots facing him, he's holding it at shoulder level.
Continuity mistake: When Foley is getting the needle ready to hypnotize Nica, right after he squirts a little out, the amount of fluid in the needle is suddenly about 75% smaller instantly between cuts. (It's not because he just squirted some out; it's instant between cuts.)
Continuity mistake: When Nica is trying to tell Dr. Foley about how she thinks both dolls are alive, when he leans forward, the lighting on his face changes from the side shot to the front shot.
Continuity mistake: When Claire is decapitated, in the first few shots, it's clear her head is going to roll away towards the door. However, after a quick cut, we then see it roll in the opposite direction towards Chucky.
Continuity mistake: When Chucky slams the compressed air cannister down, he goes from having his eyes squinted to wide open instantly between cuts.
Continuity mistake: Claire goes from facing her head up to facing sideways when Nurse Ashely comes into the room after she's strapped down. In the very next shot, she's facing up again.
Continuity mistake: Carlos' hands go from on Claire's strap to off it between cuts after he clips the final strap while tying her down.
Continuity mistake: The first strap Carlos puts around Claire moves from above to below her beltline, and then back again between cuts as she's being strapped down.
Continuity mistake: When Nica starts pounding on the window to try and get Madeline's attention, she goes from hitting it with one hand to both between cuts when the camera cuts outside.
Continuity mistake: When Madeline goes outside with Chucky, as she walks through the door, she's holding Chucky tighter to her body between cuts.
Continuity mistake: After the doctor burns Chucky's hand, when Malcolm leaves the room, there's a tuft of hair on Nica's forehead. When the camera cuts, it's suddenly brushed aside.
Continuity mistake: When Carlos is getting Nica water in the morning (after she finds the message from Chucky), her mouth goes from open to closed, then back to open between cuts.
Answer: It's been years since the injury. Maybe she transferred her soul to another doll? Maybe she repaired her head? Maybe she copied her soul into another pristine doll as she can now inhabit multiple hosts at once? Take your pick, as it's a relatively insignificant matter.
TedStixon