it seems that when you put a vertical flexbox into a grid field and you want that the flex items have a margin of 8px top and bottom that you can’t use the technique of giving the wrapper -8px top and bottom. It will only affect the top margin but won’t affect the bottom margin.
As you can see the bottom is not aligned:
Here as test the same scenario but without the use of grid. As you can see green div aligns perfectly to the collection above: