Continuity mistake: Satine and her guards along everyone else who entered the shuttle at the end of the episode disappear - you can easily see inside the shuttle and through the other window.
Continuity mistake: When Mixer and Redeye are first seen patrolling the Coronet's hold, their armour markings are visible in the first shot, but in the second, their armour is suddenly plain. (00:01:42)
Continuity mistake: When Anakin is facing down one of the assassin droids, after it throws Redeye's body at him, he and the droid are suddenly in a different part of the cargo hold, with fewer crates around them. (00:09:04)
Answer: Dooku never accepted Ventress as his apprentice, as far as I know; he just kept her as his devoted personal assassin. In Phantom Menace, it is stated that there can be only two Sith at a time, to prevent a power struggle in the lower ranks. To accept Ventress as an apprentice, Dooku would have violated that rule.