Phone forgets settings every time I switch off

[GeordieGill]

Every time I switch on my phone it has forgotten certain settings, i.e. home touch buttons (navigation buttons at bottom of home screen) revert to default, and most annoyingly sms app reverts to the pre-installed app, NOT the one I choose and have repeatedly set as default.

Any ideas, or is it a factory reset job?

 

[lvt]

My LG G4 always forget brightness setting after each restart, I guess that it's a tradition?