I can not get the nut to go back on the radiator valve/tail. Why I don't kn ow... nothing's been changed that end, it got a new TRV the other end. The nut just begins to grip a little then lets go. I've tweaked the angle of th e valve many times to try to ensure it's perfectly aligned. No joy. I've pu shed the pipe up as far as it'll go. No joy. Ideas welcome!
NT