Desktop icons move when Xfce4-panel set/unset _NET_WM_STRUT property
When using the "Do not reserve edge space" option, the shortcuts move down the screen. Some of them simply move in height and one even runs from the left side of the screen to the centre. And they move unevenly, with the top labels in place, less in the middle and the biggest shift at the bottom labels. That is, the lower they are, the more offset they will be.