Try not using beta software. Or roll back to iOS 11b5.
Beta software is the latest, but it's rarely 'the greatest'. It is not 'formally issued' code, and the whole point of beta releases is to find bugs. Beta users are expected to accept that beta releases won't work properly. If that causes a problem for them, they should stop using the beta release, and revert to a known good version.
You've found a bug. Report it to the developer of the beta software: Apple.