Created attachment 6637 xfce panel icons overlapping Some of the icons are not drawn correctly. Seems like icon itself is fine but gets rendered on background consisting of some other icon. In other words one icon is on the foreground and one is on the background (neighbor from left/right). See attachment.
Attached file presents scenario in which qnapi icon ("q" letter) got rendered on redshift icon ("bulb and moon" icon).
This is the behavior of the notification area without compositing. It should meanwhile be improved but keep in mind the notification area is deprecated upstream.