I've replicated this issue in a sample Xcode project just displaying the current time on the shield (independent of UserDefaults, so it's not related to the thread you linked). I've submitted a sample Xcode project with the app and shield extensions replicating the issue as well as a screen recording. The id is FB11673371. Thanks!

@Kmart any feedback on this issue? thanks! I've been able to replicate the issue in an independent app "OffScreen". If you start a blocking time range from 10:00-10:15, it will say "No Twitter until 10:15" and then open Twitter at 10:15. If there is another blocking time range from 10:16-10:31, the app will be open until 10:16 when the shield will reactivate and it will say "No Twitter until 10:15" when is should say "No Twitter until 10:31".

Sorry this was a typo. ManagedSettingsStore.shield.applications is set to the application that is to be blocked. When this happens while the application is open, the Shield Configuration is not refreshed. Thanks.