Here you can see the problem
On some scales (sometimes it happens in 100% scale too) elements with position: sticky create spaces.
It occurs without display: grid, but we fixed this problem locally using crutch.
We put margin-top: -1px, paddin-top: 1px and top: (needed top - 1px). It works fine for simple blocks.
But with display: grid we have horizontal and vertical spaces, witch can't be fixed with our crutch as you can see in jsfiddle
Created attachment 438644 [details]
Test case for this issue
I am seeing some cracks (I assume they are between layers) in Chrome, but not in Safari. Can you confirm that you are seeing this issue in Safari?