I have intermittent WiFi drop outs on my Smart Hub that have been going on for a while now. I've been using a Tenda Nova mesh system now for a couple of years, but the issue is exactly the same. I've disabled the WiFi on the hub, and connection is far better, especially in the upstairs bedrooms, but the drop outs still occur. I haven't bothered contacting BT for a while as the drop outs only last a few seconds, then it comes back. Last night however, I lost internet connection completely. I rebooted the hub but the lights were flashing purple (I think it's purple but can't be sure as I'm colour blind). After an hour or so it finally rebooted and has been fine ever since, with a solid blue light.
Other than powering off/on I haven't altered any settings. This is one of the reasons I don't contact support as they always suggest changing settings etc when it always corrects itself without touching a thing. I have an unused Smart Hub that was sent to me a couple of years ago, after having similar problems that BT weren't able to rectify, and I'm wondering if it's worth trying that or asking BT to send out an engineer to check the line etc?
Assuming you are still on an ADSL connection, is there any noise on your phone line? Dial 17070 and select option 2 (Quiet line test), and see if you can hear any cracking noise.
Here is a suggestion which I have found seems to fix my occasional ADSL connection issue.
Within the exchange, the broadband signal is routed through a number of mechanical relay contacts, including the Line Test System (LTS), the Line Card, and the Test and Monitoring System (TAMS).
These tend to give poor contact resistance if they are not operated for a while, and this caused low or intermittent ADSL connection issues.
One way which often clears this issue, is to ring your home number from a mobile, making sure you have a phone connected. Let it ring for about 30 seconds and then pick up the phone to stop the ringing. You can then replace the phone handset.
If you have an answering machine, the make sure it will answer the call after about at least 10 rings.
Following this procedure activates the Line Card and LTS relays and passes 80V AC ringing voltage through the contacts, and some other relays in the broadband test path.
You may be surprised at the difference it makes. This sort of issue would not be detected by Openreach, as its on the equipment side of the MDF (Main Distribution Frame), which maybe why its not getting fixed.
So far so good. Since doing as you suggested I haven't had any dropouts. If the issue returns I'm assuming I just repeat the exercise, or is this a one time only fix? ☺️
I have found it cures the problem for at least a month, I think it also depends on how often the phone is used to take calls.
Identifying the exact point where the problem is occurring, is virtually impossible. Also running a line test clears the problem, which does tend to point towards an issue within the exchange.
I have even tried passing a small DC "Wetting current" by putting a 10K ohm resistor across the phone side of the filter. This did not seem to help, as that would normally help with high resistance joints, which what made me suspect relay contacts. Activating those relays and passing 80V AC ringing current through them, seems to fix the problem.
Not sure what is going to happen when the 50V DC is removed from the line when the PSTN equipment is turned off, and calls are routed over Digital Voice. I would suspect that the LTS will still have be retained, to allow testing of the "E" side path, but no 80V AC will be present.
At least what I have suggested, may be of some help in your case.