Ghost timer after reboot
Created by: Arc676
Build: OTA4 16.04/stable Device: Nexus 5/hammerhead
If you set a timer, the interface doesn't appear to allow setting of a new timer. This leads me to believe that the app is designed to only allow one timer to be running at a time.
If the phone reboots while a timer is running, the timer is restored on power-on. This can be seen from the fact that if you swipe down and access the Time & Date settings in the menu bar, the timer is still there. However, if you open the Clock app again and go to the timer, it's gone. This allows you to set a second timer.
I discovered this by accident because the power button on my phone has some debris and jams sometimes, leading to a forced power-off. I've since been unable to reproduce this issue, both by using the power-off menu and by forcing an unclean power-off by holding the power button.
All I have is this screenshot of the two timers.