Looks like broken theming. You can easily check by installing the package shimmer-themes and setting the notification theme (in xfce4-notifyd-config) to "Greybird". That should fix it.
Looks like broken theming. You can easily check by installing the package shimmer-themes and setting the notification theme (in xfce4-notifyd- config) to "Greybird". That should fix it.