Fedora 24 Users: Don't Run "DNF Update" From The Desktop
Fedora QA is currently figuring out a bug where some users running "dnf update" from their graphical desktop are being hit by issues ranging from duplicate packages to kernel updates not working. The current hypothesis is depending upon your hardware or package set, running this command might crash your graphical desktop and with that also crash your updating process, potentially leaving the system in a troubled state.
In the meantime, Adam Williamson on behalf of Fedora QA recommends either using the offline update system or running the DNF update command from a VT -- basically, anything but a graphical desktop. More details here.