It appears this is long-running problem plaguing N5's for some time. I saw sporadical "Can't connect to camera" on 5.0.1 but after update to 5.1 (I flashed the stock image) I literally cannot get the camera working for more than 1 unlock session.
I did have root but I thought it might be a problem so I unrooted and reflashed stock, but no help. The only other thing I can imagine to do is factory reset, but I have a few security apps that will need some time to be setup again (mostly banking and 2 factor stuff), plus I am not sure if I can restore data w/o Titanium using Google's new 'Restore', so I'm keeping the factory reset as last option.
Any ideas what I can do here? Is it happening to anyone else on 5.1? Can I somehow verify it's not a HW issue? (although, it was working on 5.0.1 so it's unlikely HW issue).
The only apps which *may* be accessing camera are Trusted face unlock, Whatsapp and Hangouts. Nothing special I'd say