Hey there, KarlAlsop,
Thanks so much for using Apple Support Communities. We want to make sure that the parental restrictions you're putting in place are working as expected! The first place we'd start is by ensuring that the devices in use are all running the latest version of their respective operating system. We'll share a couple links below to help in that process. Updating can resolve a lot of issues with unexpected behavior such as this one.
Once you're up to date, if the issue is still occurring then we want to recommend setting up those restrictions once more from scratch, disabling any existing restrictions and starting over. This may help "refresh" those restrictions, ensuring that they're capturing all of the content that they should. Here is where to start with that: Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
We hope that this information is helpful.
Have a great day!