If i set the sidebar menu to relative=true there seems to be a problem with the width on collapsed dropdown items. If i change position fixed to relative in the base layout instead of setting the relative property on the component it works as expected.
Here the sidebar is relative to .sidebar_left and not your grid. remove .sidebar_left.
Check my working example on how to use the relative prop in a grid layout
If i set the sidebar menu to relative=true there seems to be a problem with the width on collapsed dropdown items. If i change position fixed to relative in the base layout instead of setting the relative property on the component it works as expected.