Screen Time removing app limits

I have my daughter (14) and son (12) under family sharing. I have screen time enabled on each of their iPhones, along with content restrictions on, and a passcode they do not know. Every few days, all the app limits I put in place (an hour on TikTok, Netflix, YouTube, etc) on the phones - sometimes both, sometimes just one - disappear. All that's left is the time restriction on the "games" category. Downtime still works, so do the content restrictions that prevent them from uninstalling and reinstalling apps, etc. This is an ongoing issue, no matter how current the updates are, how often I reboot, how often I change the screen time passcode. Any ideas on what is going on? So frustrated. Thank you...