iphone storage issue since updating to 11.2.6

I updated my iphone SE to 11.2.6 2 days ago. Ever since, I've been having huge storage issues. I backed up, reset to factory settings and restored, but it didn't help much. I have a 16 GB iphone and it says the System is using 6 GB. That can't be right. I've read other threads and can see that others are having this issue and there are replies that it is either What'sApp (I don't have What'sApp on my phone) or "corrupted data" issues, which can't be right -- lots of people across the country experiencing the exact same problem can't all be having corrupted data issues. If I've backed up & restored, what's next?