Slight checkerboard pattern when blurring mask (web)

there’s a slight checkerboard pattern in the mask when blurring a few times in a row

it’s not noticeable in the mask directly, but it shows up when using brushes or transforming

Check smooth shading.

It helps, it hides the pattern, but the pattern is still there in the polygons.

Try the same mask blur process with the normal app, I don’t think that’s a bug.