Unfortunately, you can't fix this, it's a galaxy issue. The game renders the brightest stars in the skybox first, and has a limit on how many stars it'll render, and though this can be tweaked (including with a relog), in many places the jump in density between the "cubes" is simply too high to not be visible. Take a look at these maps from
EDAstro to see the difference, the mass code F-H maps:


There's no way around this, except if Frontier remade the entire galaxy generation, which is not going to happen. (It'd break the bubble, BGS and PP, after all.)