When Daniel and Anthony get into an argument outside Miyagi-Do, Anthony's hair is straight. When Anthony is later shown inside Miyagi-Do, his hair is curly. This may have been due to shooting these scenes on different days, even though they are supposed to take place in the same day.
Anthony tells Daniel that he has no memories of Mr. Miyagi. According to Mr. Miyagi's headstone, he died in 2011, while Anthony was born in 2005, meaning Anthony would have been 6 years old when Miyagi died. 6 years old is plenty old enough to have memories of someone.
Kreese brings Silver a 6-pack of beer as payment for their wager. Kreese had won the initial bet, but Silver suggested they go double-or-nothing on Robbie and Kenny's fight. Silver's student won, meaning the debt he owed Kreese was wiped out and neither owed the other anything (hence the "or nothing" part of "double or nothing").
Devon Lee says Chong Li threw dirt into Van Damme's face in Bloodsport (1988), but that was incorrect. It was a chalky tablet he crushed into a powder and then threw it into Van Damme's face.