Plot hole: The police Inspector recounts the murders, comparing them to the ten Biblical plagues of Egypt, and he states that in keeping with this theme Dr. Kitaj was killed by rats. First, Dr Kitaj dies in a plane crash. Okay, he was attacked by rats in flight but nobody would know that - his plane crashes in a huge, violent fireball and nobody would find any rat remains after that. Second, there was no plague of rats in ancient Egypt! (Go ahead, look it up). Even if the police had made the connection between the mysterious deaths and the ancient plagues they would not make the connection here.
Plot hole: When Olive gets in the motorcycle sidecar to go to hospital to have her baby, her weight lifts the bikes rear wheel off the ground. Stan rides on the rear of the bike seat to keep the wheel on the ground. However, Stan never intended to get on the bike until this problem occurred but he was holding a motorcycle helmet from the start of this scene.
Plot hole: Major plot leak: How could Flint's ship get into the lake atop a tall volcano all in one piece? If he wanted to merely hide the treasure in order to recover it later, the whole setup, including the lake's draining system, would be totally unnecessary, and it looks all too deliberate for the ship to be sitting in the lake by accident (say, thrown in by a violent storm).