2 intersecting lines appear on desktop, however the lines appear on top of windows when a window is open. This happened on Ubuntu 16.04.4. Note: I had to categorize this and did my best so it might be an incorrect placement.
Sorry for the long time to reply. Is it always reproducible? Try to enable/disable compositing[1], does it make any difference? Can you attach a screenshot of this problem? 1 - Settings Manager (xfce4-settings-manager) > Window Manager Tweaks > Compositor > Enable display compositing
I don't have XFCE anymore so I can't answer the questions. I got rid of it because of the lines, sorry.
I'm sorry to hear that. Well, if you ever come to try Xfce again and still find this bug, please reopen.