Okay, I think you have the same issue with yours that one of these has down here. I seriously doubt glue will hold. These appear to be Delrin and, unless you have the correct adhesive it won't hold. The one I have that's split looks fine until you look under magnification. It has a tiny split. I could make a brass sleeve and press it onto the coupling. I might even have a replacement piece. No guarantees it won't split either. Might, might not.
Jay
