I have the default camera app which is a called Camera Go and GCam 7.4.104 from here. Whenever the camera starts acting up GCam won't even open. Camera Go functions but the back camera takes low res photos. At this moment in time camera is working perfectly fine but just sometimes it just starts acting up and doesn't go away for some time. It does seem to fix itself sometimes after going through different camera modes like portrait mode, switching back and forth and restarting phone several times but it's getting quite irritating.What camera app are you using? Try one of the gcam mods.