I recently got my WH-CH720N headphones for Christmas, when a few days ago the extendable part for the headphones broke. The left slide will now slide freely instead of it having the 'sections' the right side has. Is it possible to to fix this myself, or do I need to return it, and get it fixed? I've already tried to see if I can get the plastic off, but can't. I also hear a rattling noise in it, presumably from the piece that broke.