After a bit of experimenting, I've found that if the camera is opened from the lockscreen, the camera service seems to continue running after the camera app is closed. When trying to use the camera with another program, including the native camera app, shows a black screen where the camera preview should be displayed, followed by a crash of the program. The camera service keeps the phone awake, and kills the phone battery within 5 hours.
I'm running on the stock Nexus 5 ROM, with all programs and the OS up to date.
Has this been experienced by anyone else?