iPhone 8 forgets Global HTTP Proxy settings

Hey guys.

I've applied Global HTTP Proxy settings to both of my kids iPhones using Apple Configurator. I have also done the same to thier iPads. On the whole, this has worked really well but there seems to be a problem with the iPhone 8 which is running iOS 16.2.

What appears to be happening is that after a period of time the iPhone seems to forget the proxy settings. Looking at the proxy (squid) logs the requests no longer come through as an authenticated users. Rebooting the iPhone solves this.

I have to confess to duplicating the mobileconfig files and simply changing the relevant values, which has meant that the UUID's for the Payloads are identical across the 4 devices, the other 3 devices seem to hold the proxy config indefinitely though...????