the 3rd doesn't break out because, as mentioned, it can only be broken from the inside.. and the 4 made a 2nd layer of shields between them and the 3rd -- which also can only be broken from the inside; the 3rd is on the outside so he can't break them

basically i guess he has to be able to directly attack the people who made the shields to break them. and when they're enclosed on both sides in the shield i guess it can't be broken

well giving the 3rd the respectg he deserves he can probably break it, but it wont be easy and its not like he can take his eyes off oro at the moment, so i guess he's stuck fighting them

the reason the 4th didn't surface was a different one in the manga and made more sense.. i'm not sure why they changed it. not sure if they'll explain why only teh 4th didn't show up in the anime or not.. i guess we'll have to wait and see =p