Excellent points, stef7. I've always (secretly) hated reading posts to do factory resets to solve problems because a lot of replies indicated that it didn't solve their particular problem. Then the OP's are really PO'd because now they have to reinstall and reconfigure everything.
I'm only posting this because, as mentioned above, I did a reset to factory last week. While everything MAJOR was identical to what I expected (OS version, all apps and settings; plus I chose not to make any backups (I unticked backup to Google Servers and unticked reinstall apps automatically), some small things were different. Not only did the app I was hoping to get working start working after the reset (which makes no sense why it wouldn't work before but that's besides the point), but it definitely wasn't identical.
Of course my carrier's bloatware was all present and accounted for (one could hope, eh?!) but my preinstalled videos were missing. Someone else mentioned this here too in another post, but sure enough, mine were missing too. Now personally, I don't care that the videos are missing but it makes me wonder why, and makes me question if "reset to factory does not necessarily mean reset to the state when you got the phone".
This gives me a glimmer of hope that maybe, just maybe, reset to factory MIGHT fix the unexplained. Sorry to sidetrack...