Audio problem: When Max is biting down on the squeaky toy during the bullet extraction scene, the way the toy squeaks doesn't really "match" with his biting. Those types of toys wouldn't let out comically long squeaks like that from a single bite down. (Obviously it was exaggerated for comedic effect).
Audio problem: When Brooks and Max trade places during game night and Brooks taunts Max by calling him "Pretzel-boy," watch closely... Brooks' mouth isn't moving, revealing the line was added in post.
Audio problem: Annie states that her phone went to sleep while trying to find the bullet. She uses her nose to wake it up and as soon as she does that, she can be heard saying "here we go" but her mouth doesn't move.
Answer: Brooks was kidnapped by Gary's fake kidnappers. Everything to do with his kidnapping was set up by Gary. Gary did it to make people realise he'd be fun at their game night. However, Brooks was in league with the actual criminals and assumed they were responsible, which is where the mix-up happens. Eventually, the real criminals show up in the third act. Basically, it's two separate storylines that converge at the end through a comedy of errors.
TedStixon