Well. After spending about 30 minutes with a Senior Advisor, we may have identified where the bug is and how to work around it.
The bug appears to be related to making changes in the “Family” section at the top of Settings. Don’t make changes there. Make changes directly in the Screen Time section a little bit further down in Settings. That seems to have fixed our issue.
Select Settings -> Screen Time. Select the child member in that first screen and ONLY make screen time changes there. So far so good for us.
The advisor also observed the issue in Family section and has put in a defect order. Maybe a fix will come, but at least there appears to be a workaround.