Hi  @Kernow_Yardie 

If you haven't already, please check out our FAQ: How to configure Parental Control on TP-Link Wi-Fi Router for details on effectively configuring parental controls on your router.

That said, Random MAC Addressing is common on client devices these days, and can certainly undermine the effectiveness of parental controls that use a device's MAC address for identification. One step would be to disable Random MAC on those devices – just for your home network.

As for the blacklisted sites disappearing and reappearing in the app, I'd recommend making sure your router's firmware and your Tether app are fully updated. 

If they are already fully up to date, you may want to open a support ticket to see if our team can take a deeper look into what may be causing the behavior on your network.