I recently got the TF: Prime Arcee and starscream and they both have issues with ball joints. Arcee's shoulder ball appears to be too large for the socket and pops out with the slightest manipulation. I tried sanding it slightly, but i'm afraid I'd go too far. Starscream's leg joint has the opposite problem, the ball seems a tad small for the socket. Any tips for a novice to rectify the situation?