I don't know if this would help any, but if it is a real ball joint (I don't have Rattrap) you may be able to pop it out and sand it lightly to get rid of the burr. I had to do that with POTP Jazz because his leg would fall off when moving it. I sanded off the bump that should not have been there, then added a light coat of nail polish to get rid of any play I introduced in the sanding. It's working fine now.
I got a Botcon Packrat (the Generations Deluxe mold) in a trade a while back, and I was considering selling it with the new beasts coming, but I think at this point I will keep it, if only because I realized (WAY late) that it unofficially pairs with my TFSS Fractyl.
Yeah I'm gonna have to give that a try because it is really annoying.