Continuity mistake: When Alan is trapped on the floor, and the game is placed over his head, Sarah rolls the dice which fall on the lower left corner. When the angle changes they've moved further to the right.
Continuity mistake: When Alan confronts the lion with a knife, the blade is either facing flat or sideways depending on the angle.
Continuity mistake: During the stampede, when the four are watching the animals pass by the hall, Sarah is randomly next to Alan or behind him. Also, when the stampede ends, the four swap from being separate to firmly together in a mere frame.
Continuity mistake: When the pelican grabs the game, there's a wide shot of Alan running behind the bird. The damage on the side of the arch behind is bigger than it was in the immediate previous shot.
Continuity mistake: When the monkeys go into the police car, they take the shotgun and fire it through the roof destroying the roof lights, but in all the later shots of the car the lights are still destroyed, but the roof shows no damage.
Continuity mistake: When the cop's car windshield gets destroyed, he says, "my car, my car..." When he's driving Alan, more of the glass is there.
Continuity mistake: In the supermarket, right before Peter spills detergent on the floor there's a shot of his feet walking by a shelf. The corner of the shelf is spotless, yet a frame later, from a wider angle, it's all covered with garbage.
Continuity mistake: Peter says he only needed a 10 to win. Impossible. He has only rolled a 2 and 5 (in the attic).
Continuity mistake: After Judy is shot by the poison flower, Peter cradles her in his arms. That is in close-up. When it goes to wide shot, he isn't cradling her anymore.
Continuity mistake: After Alan swings on the rope and grabs the game he opens it and suddenly hears the hunter say "Don't move." During those shots the position of the pieces on the board are not continuous.
Continuity mistake: When the house is breaking in two and the floor swallows Alan, the damage to the round window is not continuous between the shots inside and the angle shot from outside.
Continuity mistake: When the movie ends and Alan becomes young again he hugs his father. The position of the handkerchief on his suit changes between shots.
Continuity mistake: When Peter sets the Jumanji game on the table for the first time, it is placed sideways in the wide shots, or parallel to the table in the close-ups.
Continuity mistake: When Alan confronts the lions, he stabs the knife on the floor facing a 4 o'clock position. when the angle changes it faces 6 o'clock.
Continuity mistake: When Peter's foot is trapped by the carnivore plant and is held up by the 3 guys, his jacket is alternately hanging loose or stuck under Sarah's arm.
Continuity mistake: When the cop is about to run Alan over with the car, first Alan is standing sideways on the road, then there's a close-up of him turned 90ยบ looking straight at the cop, then a third angle shows him turning around from the initial sideways position.
Continuity mistake: When the cop is about to encounter Alan, there are two passers-by behind the car who disappear in the close-up angle.
Continuity mistake: When the spiders show up, Alan's hair is covering his right temple or not, depending on the angle. This changes back and forth.
Continuity mistake: When the hunter crashes against the supermarket wall it makes no mess - as the final wide angle reveals, yet when the kids arrive the whole place has stuff scattered all over.
Continuity mistake: When Alan is about to cry "stampede!" several books fall on the floor. After he shouts it, there's a wide angle and the books are gone.
Answer: The game is essentially "resetting reality" back to the point Alan was first sucked into the game. So it is undoing everything that has been done - including taking away the gun and bullets Van Pelt had purchased.