In this example, there appears to be a conflict between container-type and Grid layout that when a position element overlays outside of its own cell and over a next-door cell, some stacking issues occur.
Check the Codepen link (https://codepen.io/rctneil/pen/OJErQRr) and open the Sl-Select web component in the first grid cell (Ensure on a wider viewport) and see how the checkboxes underneath show up ontop and the menu is not usable?
Does anyone have any solutions to this issue? Disabling the container-type
property resolves the issue but obviously breaks the container query that's being used.