Phone Settings menu auto-quits when trying to access most items in it (LG G2 / Kitkat)

[LG_G2]

Problem appeared today, very frustrating as almost no info online. I have an LG G2 with latest KitKat available for it. When I go into main phone Settings, it opens. After that I can still tap on one of the main 4 settings "tabs" at the top. Now, when I tap on almost any other option (e.g. Security, About Phone, Accounts & Sync, Bluetooth, etc) the settings screen just disappears and I'm taken to my home screen! I can only really get into random Settings sub-menus like Home Screen or Sound Profile, everything else auto-quits. It even shows for a fraction of a second the settings sub-menu I'm opening, but then it disappears off the screen.

I've tried rebooting, no help. I tried changing to stock home screen, thinking Nova Launcher was interfering, no help. When I press Home twice, to see recently used apps list, I tried long-press on Settings to get to "App Info" and force-quit Settings, but that stage itself doesn't work (just disappears and I'm back to my home screen).

Please, does anyone know what's going on? I really don't want to have to factory reset the phone yet (don't even know if that will help).

Thanks.

 

[LG_G2]

Small update - when I get into Safe Mode, I am able to open Settings, and access the menus I was not able to access before. What does this suggest to you? Is there something causing a settings crash during normal operation, like an app? How to diagnose it? I haven't installed any new apps for a little while, and was able to use Settings normally only a few days ago.

(Sorry, I am actually pretty techy but never bothered to really get into how Android phones work, so some of my questions may appear naive!)

 

[LG_G2]

Damn it - a new issue that's concurrent - I cannot uninstall apps. The uninstallation crashes the second I press "Yes" (confirm uninstall). I can uninstall via Google Play store! So there is something quite fundamental going on, that's wrong...