Continuity mistake: When Data starts the printing press, two closeups show the two $100 bill face templates on the machine as it prints the counterfeits, however, what is being printed on the papers are the images of $50 bills. (00:42:10)
Continuity mistake: When the Fratellis make their escape in the ORV at the start, the windshield's rearview mirror disappears and then reappears. (00:03:00)
Continuity mistake: On the deck of the Inferno, when Mama is pulling the pearls from Mouth's mouth, Francis is tying up Andy's hands with black rope. When Mama asks, "Is that all?" the color of the rope is off-white, but it then changes back to the black rope in the following shots. (01:32:30)
Other mistake: After the kids find Chester Copperpot's skeleton, Mikey picks up Copperpot's book and finds the Gehrig baseball card inside. When Mikey turns the card over it's the 1973 Topps Lou Gehrig All-Time Grand Slam Leader #472 (which has nine players' grand slam stats listed on the back of the card, that includes Hank Aaron who started playing MLB in 1954). The problem is Copperpot was reported as missing in 1935, but this specific Topps baseball card (now well known) was issued in 1973, nearly 40 years after Copperpot's death via the pirate booby trap. (00:54:30)
Continuity mistake: When Francis Fratelli pours the gasoline in front of the County Jail, there's a parked police cruiser at the corner of the building next door, in front of its windows. After he ignites the fire, there is a close-up of the ORV's tire as the vehicle pulls away, and in the background that squad car is gone, but in the next overhead shot that parked police cruiser is back. (00:02:10)
Continuity mistake: When Mikey turns the 'triple stones' and triggers the large ball, the ball is stained and dull-colored when it begins to roll, then changes to a clean, high-gloss brown as it continues on the track, but reverts back to its original coloring when it falls. (01:10:45)
Revealing mistake: When Chunk unknowingly flags down the ORV driven by the Fratelli brothers, as Francis drags Chunk to the back hatch there are cables that run from the ORV to the side of the road, off camera. These cables were not in the previous shot when the ORV first stopped.
Revealing mistake: Up in the attic, when Chunk walks over to Mikey (who wants Chunk to drop the frame), at that moment Data and Brand are alone, and while the two of them are looking at the plasma lamp Brand flicks the glass with his finger, and just as Data stares at Brand we can clearly hear Data say, "Don't touch it Josh!", which is Brand's real name. (Mikey does the same thing later at the lighthouse restaurant.)
Continuity mistake: In the beginning, when the Fratellis are eluding the Police, Chunk witnesses the chase. In the first shot the slice of pizza is on the window. Next shot Chunk holds it in the air, and in the third shot the pizza is back in its place where it was in the first shot, with a saucy smear on the window. (00:04:10)
Revealing mistake: When Troy is in the country club restroom, the toilet overflows and he gets pushed up to the ceiling, you can see that he is sitting on a platform. When the water shoots out, you can see the pole connected to the platform being raised up.
Continuity mistake: When Data's 'bully blinders' are on, just as the bulbs dim, in the close-up Data's cartridge holder hangs over his right shoulder to his left hip instead of the opposite way, as seen in the previous and following shots. Interestingly, this is not due to a flipped shot. (00:48:20)
Continuity mistake: In the scene in the basement, Chunk is about to drink from the water cooler bottle that is mostly empty. When he stands up and tries to catch it, it's more than half full. (00:40:25)
Continuity mistake: At the start, when Data practices with the blue suction dart, in the close-up as the dart flies out we can see the mechanisms inside Data's invention. When it cuts to a tighter close-up, suddenly there is a spinning spool welded inside, which was not in the previous shot, that is retracting the orange string. (00:03:50)
Other mistake: When the Fratellis get out of the water, they show no signs of being wet at all, like when they catch the Goonies near One Eyed Willy.
Revealing mistake: When the Fratellis get a visit from the bats out of the basement, two bats fly in front of Jake Fratelli and while they are flying in front of him you can clearly see their wires.
Continuity mistake: When the kids light the two lanterns they find in the pipe room, they stay lit somehow, even though the lanterns get wet in the well.
Continuity mistake: Before the 'bathroom' break, when Mikey holds up the map, the top of it is burned off and very few musical notes are actually there along its edge, but when they reach the skeleton's bone keys the top of the map is clean, with a musical score along the entire edge. (01:29:30)
Continuity mistake: Chunk breaks the glass on the frame and then he and Mikey clear away much of the broken glass from it. When there is another view of the picture all the glass is still on it.
Revealing mistake: At the Astoria Country Club, when Troy first sits down in the stall and opens the magazine, behind him are at least nine columns of small patterned tiles. In his next close-up as he looks around, the wall behind him is completely different. Now there are only six columns of larger unpatterned tiles, with a long vertical gap between the tiles (where the grout should be) - which is the track for the mechanism to lift Troy in the following shots. (00:51:00)
Continuity mistake: When Andy begins to lose it in the tunnel, Brand holds one lit lantern at the head of the line and Mouth holds another lit lantern at the back of the line (Mikey holds an unlit lantern). Next shot the lit lanterns have switched, just as they reach Chester Copperpot and Andy screams. Then in the next wideshot before it pans to the skeleton, the lantern Brand holds up switches yet again. (00:53:15)
Answer: According to Mikey and Mr. Walsh, one of his crewmen must have taken the map and fled when One Eyed Willie was murdering his crew. This is substantiated in the novelization.