Continuity mistake: When Matilda's family is speaking out numbers and summing them up, the mum places a can of beer on the table that moves around between shots.
Continuity mistake: On Matilda's first day of school she gets off the car wearing a sweater and holding a notebook but them is shown just wearing her blue dress.
Visible crew/equipment: When Matilda makes the pitcher fly up in the air you can see the shadow of the stick that was later deleted and erased.
Character mistake: When Harry takes the kids to his business, he's showing them how he "restores" cars. After putting the bumper on, Harry says, "Transmission. The sawdust quietens the gears and let's the engine run as sweet as a nut." Putting sawdust into the transmission would not change how the engine runs as they are two separate components. It may make the transmission quieter but would have zero effect on the engine.
Answer: He has been receiving and selling stolen car parts.