Why grid helper looks dotted when pixel ratio is over 2?

Hi, I not sure why Grid helper looks dotted when pixel ratio is over 2, and also a feel like the threejs default antialiasing is not working property, when pixel ratio is 3 or more.

Any idea how I can solve this?
Any help would be appreciated, thanks.

Pic at pixel ratio 1

Pic at pixel ratio 3 (dosent looks good for me)