You will lose everything you've customized in your phone, but you will not lose anything associated with your account. Hence, after resetting your phone to factory defaults you should no longer see any of your files in your phone. But as soon as you use the same Microsoft account for that phone, everything associated with that account should be readily accessible.
You're right in enumerating what gets downloaded back into your phone (if enabled): photos, contacts, mail, most of your SMS, app settings (for supported apps or apps that have that feature) and custom settings. As for videos and music, haven't seen an auto-upload feature for those two.
There's one thing you'll lose though (I just remembered now): if you've linked accounts that span multiple contact accounts, you'll most probably lose some of those linked contacts especially those who have strange Facebook names (names that have nothing to do with their real name like "Awesome Jack" whose real name is Philip Stewart). So if you have linked a certain contact from your Twitter account to your Facebook account, that link may be lost - you can always relink your contacts anyway.
And yes, resetting a device to factory defaults is usually the last resort solution when all other attempts fail (such as restarting the phone and performing a soft reset).
BUT before you go forth an perform a factory reset, you may want to inspect your app list an uninstall certain apps that you no longer use regularly. It has been reported in a few threads here that the Discovery News app is causing that same issue for a Lumia 92x, so if you have that app you may want to uninstall it first and confirm if he's findings are correct. In addition to that app, having Kid's Corner and any of Microsoft's Beta Lock screen apps have also been reported to be related to that issue.
07-22-2015 12:24 PM
