User-Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:50.0) Gecko/20100101 Firefox/50.0
Moving both sliders to the far left in the modal window for Repeat Keys in Universal Access settings causes following desktop logins to fail. Resetting the corresponding values with dconf or gsettings from a TTY before trying to log in resolves the problem.
Steps to Reproduce:
1. Open "Universal Access" window
2. Select "Repeat Keys" button
3. Verify that "Repeat Keys" is enabled
4. Move both sliders in "Repeat Keys" modal window to the far left
5. Log out (or reboot) and try to log back in
Only a background and the mouse pointer will be visible for a few seconds before returning to the login screen. Logging into a desktop session was not possible. Navigating the login screen and switching to and using other TTYs was still possible.
The users desktop session should have been displayed.
My computer is a Lenovo T550 laptop.