I tried this and worked on my Ultra 2. No reason why it shouldn't on non ultra. I tested with 3rd party compass apps and all could save waypoints and showed lat+long. So it is a watchOS 10 problem, software problem, not hardware. First check is see if lat and long are showing on watch, if not, then its an issue. Do this. Uninstall compass app from iphone. reboot iphone. You will notice compass on watch disappears when you do this. When iphone is on again, reinstall compass app. reboot iphone. when iphone is on again, go to settings>general>transfer or reset iphone>reset>reset location & privacy>ok>exit settings. reboot iphone. when all this is done. force on/off watch. when watch is on again, you will see the compass app. Go in and see if lat and long are showing, it both are there. Problem is solved. You should now be able to add waypoint and use backtrace(on the ultra).