You appear to be using the smart WiFi where hub selects the WiFi channel so if you get a WiFi analyser on phone you can check the channels in use near you then manually select your hub WiFi channels which are free or less congested and see if the helps
Checked the network for the channels and everything seems alright.
Also tried changing modes, thinking of asking for another new SH2 Maybe it'll fix things.
Just to be clear you did switch the 5g channel off? And then try selecting a channel on 2.4g?
Update, got a new hub and nothing has changed at all. Still the same issues. I had a BT home tech come over and he's also very confused to why its saying the WiFi signal is poor, he suggested I get a new hub ( Hence the new hub update) here is a the photo