@disconnekt - I feel your pain! I have abandoned the attempt to set limits on individual apps for now. I've had to adjust my approach to be less granular and I end up having to approve more requests from my kids. I did verify, however, that logging the child's phone out of iCloud, and then logging back in, does fix other problems, like failing to update rules or failing to update the time reported back to my phone.
Did you notice that time request approvals no longer work from the Apple Watch? Approving from the watch does nothing. I must do it from the phone now. :-(
I will post an update if I learn anything new about this topic. Good luck!