The title pretty much explains it. After the 3rd sealed Oro's arms, he was not able to use them even in battle (as expected). As soon as he got into a new body however, he was able to use his arms again! Now that is quite weird, considering that the third cut his SOUL's arm off, so i would assume he wouldn't be able to use his arms even if he transferred to another body.
Even if the seal sticks to the old body why is Kimimaro still able to use his hands? What happened to the third's seal? did it simply vanish into thin air, and how was oro able to do the body switch jutsu without his arms?
Perhaps the third should have just cut off oro's soul at the neck and detach his head, that would have ended it off much more quickly and saved us several dozen chapters of Oro chasing