Created attachment 9291 
Screen shot showing network manager popup offscreen

I run an up-to-date Fedora 31 OS with the xfce desktop. I have the panel across the bottom of the screen with a notification area on the right. When I move the mouse over a notification icon the corresponding popup often appears positioned mostly or completely off the screen. For example, in the attached screenshot, the mouse is over the network manager icon and the popup is mostly "below" the screen.

$ uname -a
Linux  ### 5.3.12-300.fc31.x86_64 #1 SMP Thu Nov 21 22:52:07 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

 $ dnf list installed xfce*
Installed Packages
xfce-polkit.x86_64                            0.3-3.fc31                 @fedora
xfce4-about.x86_64                            4.14.1-1.fc31              @fedora
xfce4-appfinder.x86_64                        4.14.0-1.fc31              @fedora
xfce4-battery-plugin.x86_64                   1.1.3-1.fc31               @fedora
xfce4-clipman-plugin.x86_64                   1.4.3-4.fc31               @fedora
xfce4-cpugraph-plugin.x86_64                  1.1.0-2.fc31               @fedora
xfce4-datetime-plugin.x86_64                  0.8.0-1.fc31               @fedora
xfce4-dict.x86_64                             0.8.2-3.fc31               @fedora
xfce4-dict-plugin.x86_64                      0.8.2-3.fc31               @fedora
xfce4-diskperf-plugin.x86_64                  2.6.2-1.fc31               @fedora
xfce4-eyes-plugin.x86_64                      4.5.0-22.fc31              @fedora
xfce4-fsguard-plugin.x86_64                   1.1.1-1.fc31               @fedora
xfce4-genmon-plugin.x86_64                    4.0.2-1.fc31               @fedora
xfce4-mailwatch-plugin.x86_64                 1.2.0-22.fc31              @fedora
xfce4-mount-plugin.x86_64                     1.1.3-22.fc31              @fedora
xfce4-netload-plugin.x86_64                   1.3.2-1.fc31               @fedora
xfce4-notifyd.x86_64                          0.4.4-2.fc31               @fedora
xfce4-panel.x86_64                            4.14.1-1.fc31              @fedora
xfce4-panel-profiles.noarch                   1.0.9-1.fc31               @fedora
xfce4-places-plugin.x86_64                    1.8.1-1.fc31               @fedora
xfce4-power-manager.x86_64                    1.6.5-1.fc31               @fedora
xfce4-pulseaudio-plugin.x86_64                0.4.2-1.fc31               @fedora
xfce4-screenshooter.x86_64                    1.9.6-1.fc31               @fedora
xfce4-screenshooter-plugin.x86_64             1.9.6-1.fc31               @fedora
xfce4-sensors-plugin.x86_64                   1.3.92-3.fc31              @fedora
xfce4-session.x86_64                          4.14.0-1.fc31              @fedora
xfce4-settings.x86_64                         4.14.1-2.fc31              @fedora
xfce4-systemload-plugin.x86_64                1.2.3-1.fc31               @fedora
xfce4-taskmanager.x86_64                      1.2.2-3.fc31               @fedora
xfce4-terminal.x86_64                         0.8.8-2.fc31               @fedora
xfce4-time-out-plugin.x86_64                  1.0.3-1.fc31               @fedora
xfce4-verve-plugin.x86_64                     2.0.0-22.fc31              @fedora
xfce4-weather-plugin.x86_64                   0.10.0-1.fc31              @fedora
xfce4-whiskermenu-plugin.x86_64               2.3.3-1.fc31               @fedora
xfce4-xkb-plugin.x86_64                       0.8.1-22.fc31              @fedora