Hi
One possibility. The DeskTop.ini file may have become corrupt. This is a system file but is safe to delete as it will be recreated as needed by the system.
If you want to try this out. Open file explorer at the DeskTop and set view options to show system files. RENAME the DeskTop.ini file to (say) XXXDeskTop.iniXXX and reboot then examine the folder to see if any difference.