Widget lag on iphone 8

I bought iphone 8 in the beginning of October.

After about one week, the widget lag showed up and keeping giving me trouble.

Every time I swipe to the widget screen (the left page of notification center), the system lags for about 1~2 seconds.

This is very annoying issue because I can't use widget to see info and this will influence my usage when I have emergency to use some functions but swiping into widget screen and stuck there.

I already tried all the following methods that Apple people told me.

1. Reboot

2. Reset all all settings

3. Reset all content and settings and restore to my previous backup

4. Reset all content and settings and set this iphone as a new iphone

5. Update to the latest FW version

6. Reset all content and settings in DFU mode

7. Reset all content and settings in Recovery mode

I've tried everything that your people told me and this issue keeps showing up again and again. And actually widget lag is only one issue of this product. The whole system is actually lag when this issue showed up. The system will stuck in the full screen mode when I see full-screen videos. Every app will start lag when this issue happens. This is very frustrated. I feel like I spent money on a phone worse than Android.

I bought 4S => 5S => 7 and now 8. iPhone 8 with iOS 11 is the worst experience I have. Can somebody please help me with this?

Paul Chen