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In any of my projects, if I am using a master page with a Page Header object, then add a Layout Grid set to use the CSS grid system, the grid's gutters are not maintained when the view switches to other than "default" (e.g., 1024px or smaller).

Is this loss of gutter by design? (I have a sample project demonstrating this available here).

You are right, this is not correct.
It will be fixed in the next update.