I agree, one way find out change wallpaper!Is it possible it's the wallpaper? Somehow it seems so to me.
Put phone in safe mode see if it still thereno, it is just a plain black wallpaper - nothing on it
Press power button, once power device shows up on screen long press until says safe mode then tap it , and to exit out just reboot the phone.safe mode? ...how to do?
Try resetting launcher , clear it's data,cache, force stop. Or reset settings , to that go settings >general management >reset >reset settingsno difference with any wallpaper - still there