I bought this brush second hand a long time ago on eBay. It had served me well and finished up out of rotation in the back of the bathroom drawer. I started using it again but it felt like the knot was half full of soap. I could only use from the black ring up. I tried giving it a spa and a comb but the knot wouldn’t free up. I finished up combing the knot right out of the handle. The knot won‘t free up in the middle of the knot to glue back in. Has anyone re-knotted one of these Wilkinson Swords before and what knot to you use? Without a digital micrometer I am measuring a 20mm hole.