Screentime recording/reporting not working and therefore child screentime limits ineffective

For some reason the screentime recording/reporting on my son's phone no longer seems to be working correctly. Even though I know his phone is completely turned off at night, screentime still reports his phone as on and 100% screentime over this period. Therefore the pre-set child screentime limits are ineffective as (depending oh what the specific screentime control is) it thinks he has already exceeded them as soon as he turns his phone on. This is very frustrating for my son and I.

Looking back screentime first started to go wrong in early November 2024 and I was hoping Apple would have just released a software fix for what appears to be a bug but nothing has changed with this since then, despite a few software releases. Please advise if there is a way we can make this work or if this is a known bug with a scheduled fix release date?