I’m having this same problem and couldn’t find all the posts you said were online somewhere.
I’m also not sure whether or not the yellow piece I can see deep in the socket is the one you’re referring to or not. There is still a yellow piece inside the tip of the plug & therefore at first I didn’t think it must have broken. But when I shone a light down into the DC-in socket, sure enough, I could see a yellow piece deep in there. Was that already there or is that a broken piece stuck in the camera? I have only one camera to look at so I can’t know.
Thanks much for posting on this subject and for any help you can offer.