Waypoints Galactic map?

So I’ve searched through pages of visited systems to find a 3* mining economy. Set a waypoint on it. Go to galactic map, select ‘custom waypoint’ and then move along the line trying to find the system. I just get so far one way and then a dead end all I can do is move back to where I started. Wtf? Trying to explain further, if I want to find system”z” which I’ve way pointed in discoveries all I can do on the galactic map is go (e.g) D-E-F-G-H-J-K. That’s as far as I can move the selection along the galaxy map. I then Warp there assuming that’s as far as I can warp light year wise. Bring up map again and all I can then do is K-J-H-G-F-E-D. How do I actually get to desired “Z”? Driving me spare. Thanks