When compositing is enabled in Xfwm4, it tends to screw up my desktop icons. For example, the desktop will stop updating correctly after a while, and trying to move the icons will leave a "trail" of blue squares behind. Starting up, the icons sometimes have duplicates stacked on top of one another. This only occurs when running the Xfwm4 compositor.
Created attachment 1518
Picture of issue
Apparently, this impacts the panel as well. Here's a screenshot of it in action.
I am afraid that I have never seen any such behavior.