All you can do is for now visiting this page:
- Select iPhone or whatever product this issue affects you on (I picked iPhone)
- Fill out the personal information
- In the “Feedback Type” dropdown, select “Bug Report”
- In the “Comments” box, I wrote “Please refer to this Apple community forum for my specific issue: Screen time bug after updating to iOS 18. – Apple Community
Hopefully, if enough of us bring this to Apple’s attention, a fix can be made.
Sadly no new updates or fix yet.