Understood. I don’t think this has occurred for me much if at all but I understand what you say. I do think there is something relevant about having an unsecured WiFi connection and still having ones Mobile data connected. As the operating system may be doing something via the mobile link despite having that WiFi connection. I’ll play around with these settings next time I’m away from home (only time i need mobile data).
I also set my phone to ‘Low Power mode’ in the hope that it tries to do less syncing etc. when on mobile data. Also I note that in my iphone’s WiFi connections when you tap the ringed ‘i’ you see an option for low data mode. interestingly it says the following and I quote.
“Low Data Mode helps reduce your iPhone data usage over your mobile network or specific Wi-Fi networks you select. When Low Data Mode is turned on, automatic updates and background tasks, such as Photos syncing, are paused.”
So I might also try setting this when i get a wi-fi connection when out and about from a hot spot to see if this makes a difference (and do the same activities with it set , then unset). Funny how this option mentions mobile data when in a WiFi setting area.
I’ll keep playing as this is clearly not obvious… to be continued. Cheers