iPhone freezes in Mobile Data settings

My iPhone 7+ freezes whenever I enter Settings>Mobile Data. Not sometimes. Every time.

The reason *seems* to be that ios is populating the Mobile Data app listing. You get the little wheel going around but it just goes on for ever. Changing *any* setting is not possible until that list is populated with all the apps. I need to change settings quite regularly as I travel a lot and need to change the apps that can use mobile data. (I know that on some iPhones, this section is called 'Cellular Data')

While this 'freeze' is happening, the clock at the top of the screen also freezes.

This seems to be able to go on indefinitely (record is 17 minutes before my patience runs out and I stop it)

If I turn the phone off and then on again it seems to work OK then, but I really shouldn't have to reboot my phone to make simple settings changes.

I'm using ios 11.4.1 (15G77) and the model number is MN4W2B/A. This happens when I am on wifi and when I am on mobile.