Help with a knee joint problem -edit- photo added

Sorry if this is in the wrong forum, I stewed over it for a bit, but couldn't be sure whether to put it here, Large dolls, or Customizing, so I decided to play safe with General.

Anyway, here's the problem. I have an Isao2, I haven't had him long, but it's come to my attention that there is something wrong with his right knee joint.
When I move his left knee, it moves smoothly, and doesn't lock until its at 180degrees. But the right knee ... after I move it about 80 or 90 degrees, feels awkward to move, and clicks down slightly. Once the knee is locked at 180, instead of the ball-join rotating like it should, often the ball-joint comes completely out of the socket.

I've stretched the joint out to take a look at it, but I can't see anything wrong with it, it appears to be the same as the other leg.

Has anyone got any idea what the problem might be, or how to solve it?
I suspect that either the ball-joint is a tad too small somehow, or the socket is to wide ... but that can't be right can it?

*edit* My camera arrived at last! So I took a couple of quick photos before I go to bed. I can take more photos in hte morning if that'll help.

 

Glue? *makes newbie eyes* I didn't know the joints had any glue in them ops: I literally only got him a couple of weeks ago, and I've been soooo busy with a major commission (which ends soon, thank God) that I haven't really had much time to spend with him But now that you've mentioned it, I've taken a look deeper inside the joints and along the strings with a torch, and I think I know what you're talking about now. I didn't have a camera when I first posted this thread, but i was expecting one to arrive in the post soon. It actually got here this morning, but my other half ordered it, so I'm gonna wait 'till he gets back to open the parcel. As soon as we've got it working, I'll take some snaps of the problematic leg and post them.

 

Hmm, I'll pm her and ask her about it then, thanks very much ^^ I hope I don't have to send him back to volks for repairs so soon after he got here! Or just his leg for that matter. Somehow it seems really cruel taking his leg away ^^;; Perhaps I could make him a temporary peg leg whilest the other's in the post *envisions Kibou as a pirate XD* I've got a funny feeling Mutehoney might be right about the glue though - just a gut feeling mind.

Thank you both!

 

After talking to Ayaka about her attempts with Volks, it looks like there's nothing I can do about it :cry: But, none the less, I'm not going to give up. I'm going to have my first attempt at re-stringing him today. Perhaps that'll solve it, or give me better insight into the problem. *crosses fingers*