Apple has just released iOS 12 Beta 2. The new update fixes a lot of broken things from the Beta 1. Many of the Screen Time problems have also been fixed on the Beta 2. But the fixes come at the cost of losing out all of your current Screen Time settings.
Once you update to iOS 12 Beta 2, your Screen Time settings will be reset. You’ll have to set it up again. If the current Screen Time data is dear you, make sure you take a screenshot of the Screen Time stats on your iPhone before updating to iOS 12 Beta 2.
Thankfully, the App Limits you set under Screen Time settings will remain. You won’t have to set them up again.