Morning of Saturday 21st Aug, my daughter complains that the "iPlayer Kids" app won't open on her android tablet (disaster!) From there, it seems like I'm getting slow or unresponsive performance on some things, but not most things. It's mostly certain apps on Android mobiles/tablets. Switch to 4G and it works immediately however.
I've tested over two android phones, one android tablet, laptops, TVs and PCs and it's only the android apps and google home responses that are affected.
Tested using two different Smart Hub 2s (had a spare from a trial).
Tested with and without Complete WiFi discs connected.
Tested with and without additional wired switches connected (got home wiring to a number of switches in my home).
Then its probably just wifi interference. Lots of non-broadband devices use the 2.4GHz wireless band, and some of those can cause lots of problems. Also SkyQ is known to cause issues, so perhaps someone nearby has just had it installed? You could try a different wireless channel to see if that helps.
There is nothing on the BT network which would cause Wi-Fi issues, without affecting wired connections. Is there anything you have bought recently, that may be causing Wi-Fi interference, as some device can occupy multiple channels causing very slow connections?
The fact that it affects both your broadband connections, would point to something causing Wi-Fi interference, so you may have to look at what you have within the house, perhaps turning off individual electronic devices.
I live in a rural village, in a detached house, there are no interference causing changes inside my home and I'm pretty sure no one has put up a new mast that mean suddenly and consistently certain types of traffic are slow or unresponsive, whilst others are fine, and I've never had a fault or issue like this in 4 years.
If it were interference, you'd expect degradation of service on things like netflix and youtube, but they're both fine, whilst the iplayer app is not. On the XBOX app, it specifically the images (which are tiny) that aren't loading, but the rest of the app is fine.
For reference, my main mobile phone is a Samsung Galaxy S9 running Android 10. The tablet is a Samsung Galaxy Tab A (2016) running Android 8.1.0. Both are having problems. There's also a Pixel 2, and another Samsung phone, so all Android, but at least two different versions.
All combinations of the above have problems with network functions on certain apps, and I can't currently issue google assistant commands to my 2x Nest Hubs or 2x Nest Minis. Location in house, proximity to hub, other electronics, and use of complete wifi discs doesn't seem to have any impact.
HOWEVER - if I connect these devices to the BT WiFi network being broadcast from my own hub, all the problematic apps work fine. The devices are in the same locations, the hub hasn't moved.
Tomorrow someone with an Apple device is coming to my house, so I'm going to run a few tests with that. I'm also going to have one more go at disconnecting everything from my home network, powering down everything in the house, and move the hub as far away from any possible interference causing equipment, to see if that achieves anything.
I tried asking my neighbours for any similar results, responses were limited, one person said they were also having problems with the BBC News app on an Android device, but it's just one report and I don't want to rely on that as part of figuring this out.
(For what it's worth, I've previously worked on the launch of a number of BT's hubs and on aspects of broadband diagnostics. I am by no means an expert, my role was not especially technical, and this problem is beyond my understanding, but I have a reasonable understanding of the 'own domain' problems that would affect WiFi signal, and that's partly why I have some confidence that's not what's going on here. I am open to being challenged on this though - if anything that would be an easier conclusion!)
Ok final update for now, tried swapping the hub again, two new complete wifi discs, and tried powering everything down in the house and moving router to minimise interference, but even in this setup and with a device right next to the hub, the problem remains.
Problems with data/network access on certain apps, across three Android phones and one Android tablet, all different models and at least two or three different versions of Android. Services either fail to load, take a very long time to load (minutes instead of seconds), or partially load (e.g. text but not images). Lots of similar apps (e.g. other video streaming apps) working as normal however.
I only use this tablet for streaming (i.e. netflix or NFL gamepass) so the tablet itself has very few apps or any files stored (i.e. pictures). I have gone through and removed so many standard apps that I just don't use to see if that would help however it doesn't.
I have the 8 inch Tab S but since upgraded with S4 and S7+.. the original Tab S doesn't get much use now because of lag (as you are experiencing). Your best bet may be to flash it with custom ROM however I haven't done so myself so can't provide you any good advice on that, sorry.
Mine is doing the same, I do a factory reset every few months, but it hasn't been having any effect more recently. It could be the battery limiting the speed or something, but I think it is just the most up to date apps are too taxing for it these days. All I run is Netflix and YouTube Vanced, and even then, its painfully slow to use.
Likely that the slow down is related to heat. cpu is throttled as heat increases.
The heatsinking inside the case is fairly lack lustre.
If you're willing to open the back cover, replace/improve the thermal pads.
Custom ROM like lineageOS can improve things, but not all apps/funcationality work (video recording)