When Unicello flips the card behind his hand (in the opening restaurant scene), it is a five of diamonds before he does the "trick", but a four of spades when we see it from behind.
At the Coliseum: When Marco agrees to wait for Simon Templar and Sue Inverest he gets in his taxi and it moves off...without the engine starting.
When Tony is giving directions to the governor, he tells him to drive to kilo 45 where there will be a dirt road "running off to the left". When Simon and the governor drive up to kilo 45, the dirt road is on their right, and that is the direction they turn.
American tourist Eddie Hammer first says he's from Missouri, but then a few minutes later he claims to be from Indianapolis, Indiana.