Continuity mistake: The Resolute's bridges are missing their red colouration when it arrives at Ryloth and moves to angle its hull towards the Separatist ships. (00:20:51)
Continuity mistake: When three starfighters fly from the Defender to the Resolute, the Resolute's bridges are missing the red colouration on their tops. (00:15:23)
Continuity mistake: When the three Jedi Cruisers are shown after a vulture droid crashes into the Resolute's bridge, the one on the left, the Defender, has had one of its two bridges destroyed. After a cut to a different shot, the next shot of the three ships as they turn to retreat has the Defender with both bridges intact. (00:06:28)
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.