I always have the plasma-desktop configured to show the "Desktop"-folder.
After updating to Kubuntu 15.4. changes to the file-system are not to be seen on the desktop.
For example: After deleting a file from the desktop it will persists on the desktop. Trying to delete it again kde shows the error "file or folder /home/.... doesn't exist".
After right click and select "refresh desktop" the deleted file disappears.
Same behaviour with file or folder creation and renaming.
Version KDE Frameworks 5.9.0 coming with an upgraded Kubuntu 15.4.

Which version of Plasma? If 5.2, can you update to the 5.3 version (in the backports PPA) and see if it fixes the issue for you?