Continuity mistake: After the shuttle has crashed, there are four surviving clones accompanying Jar Jar. From the beginning of the fight with Turk Falso's group to when they escape out of the large geyser before it goes off, the number of clone troopers keeps fluctuating between four and three, before it stabilizes back to four when they go after the pirates. (00:10:34 - 00:12:03)
Continuity mistake: When Jar Jar and one of the clones are shown burying Kharrus, a creature walking by in the background disappears between the shot where Commander Stone is looking at what's going on and the following close-up. (00:08:53)
Continuity mistake: The clone troopers accompanying Jar Jar and Senator Kharrus are members of the Coruscant Guard and all have the unit's red armour markings. But in the middle of the sequence where the shuttle comes under attack, as Jar Jar is flung down the hallway, the troopers sitting across from Kharrus and Commander Stone have unmarked white armour. (00:04:33)
Continuity mistake: When Obi-Wan and Anakin snap "YES!" in response to Dooku's question, Obi-Wan's hands, cuffed together with a pair of handcuffs linked by an electrified cable, have somehow moved so the cable on his waist chain is inside the circle of his arms, despite that not being the case when he came to inside the cell earlier in the scene. (00:01:36)
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.