I've been on SlimSaber (SlimKat unofficial by fusionjack) and never once had this issue in quite a few months. However I've also tried 4.4 pac, beanstalk, spirit rom and probably others that I've forgotten without this problem.
To ask the obvious, you do install these roms with a full wipe right? The other thing, are you using the official aosp camera that comes with the rom? Or another app that uses the camera (e.g snapchat, instagram for example? There's a bug with the nexus 5 in which the camera will sometimes crash when using it with a third party app. I guess it's possible for this bug to filter down to our device... As I don't use any such apps I can't comment on my own experience with that. But google that issue to read more, you'll find plenty on forums about it.
Sent from a galaxy far, far away