While a pain in the ass Mendip, I'd backup all your photo's (If you do not use Google Photo's) and take the phone back for replacement. Then spend a few hours adding in your contacts and DL the APPs you use or want.

I say this as you might get the issue to go away near term but if it pops up again later after the warranty expires, you will be out money to repair it (If repairable).

Good Luck