3km View distance bug. Fix and probable cause
The bug causes grids to become invisible or not be *directly viewable beyond 3km. (*you can see the object by angling your view to see it at the edge of your screen beyond 3 km from the grid.)
The bug is caused by either creating or setting a world to Private, Friends or Public. Offline worlds are not affected. In the game settings, it will display the view distance as 'Custom'.
The in game settings can be set by default to 15 km. However in the Sandbox.sbc file ( located E:\Users\(your user name)\AppData\Roaming\SpaceEngineers\Saves\76561198103577718\name of save ) the settings do not update to 15 km and are instead set to 3km (3000). There are two settings which affect this. Sync Distance (default 3000), and View Distance (default 3000). When one is changed to 15000 and not the other, the bug will persist. When both are set to 15000, the bug will be gone or 'fixed'.
From what I think, the game isn't updating the sbc file for view distance and sync distance when they are changed in the advanced settings menu.
For players wanting to fix this bug, follow the above. Find the sbc file, which should either be named survival.sbc or sandbox.sbc and alter both sync distance and view distance values to your desired viewing distance.
Thanks to Malware (Modder/ Scripter on Keen Discord) for help.