Continuity mistake: When Obi-Wan says, "Unlike you, maybe he's getting some much-needed rest," he's stroking his chin with his hand. Mid-sentence, the scene cuts to a closer shot of Obi-Wan, and his hand changes position. (00:02:50)
Continuity mistake: When Rex pulls off the helmet of the disguised commando droid, Cody is missing the piece of armour protecting his right thigh. (00:09:37)
Continuity mistake: Before the clones retake the base, they have just enough blasters between them for all five of them to wield one each. When Rex is dealing with the commando droid captain, his left holster still has a pistol in it even though he loaned his other pistol to Cody. (00:14:00)
Continuity mistake: When Rex starts giving the rookies a pep talk, as well as in the shot afterwards where all the clones grab their helmets, Echo's helmet is missing the binocular attachment. (00:16:28)
Continuity mistake: When Grievous calls a battle droid who asks if the Rishi station's destruction was a good thing an idiot, the clasp of his cloak is missing. (00:21:15)
Continuity mistake: During the end scene, when Echo and Fives are honored for their services, in the first shot, Echo's helmet is missing, despite his arm being positioned as if he's holding it. When his helmet appears, it's missing the red binocular attachment, which only appears later in the scene. (00:22:00)
Answer: I guess that 1) the King assumed that Ventress' droids were meant to capture the Jedi, not kill him outright. When she yells at OOM-224 to shoot Yoda, she evidently failed that expectation. 2) Sending out a bunch of Droidekas after it is plain that Master Yoda has clearly won is not a sign of good sportsmanship, either.