Got round to taking a look at mine today. As you can see it's pretty clearly been running on just the outside edges. Got an old wet polishing stone and ran up and down the length of it for a while with nice even strokes until the finish seemed uniform being careful to make sure the stone remains flat the whole time. Kept going until I was happy with the finish, cleaned it up and put it all back together and adjusted it. I must say, I'm pretty impressed, the level of grip the rod has on the draw tube now is massively improved. Everything feels much more positively engaged while remaining firm but smooth. I haven't used it in anger yet but just testing it by running it in and out and some light pulling on the draw tube seems very promising! Thanks ever so much for your help. One less worry now!