Intermittent connection issues loading/changing site- secure connection failed/site can't be reached

[EDIflyer]

Is anyone else occasionally getting a 'connection down' error from Chrome (or 'Secure Connection Failed' from Firefox) when changing page - if I hit refresh it works fine. At first I wondered if it was the site I was using but have noticed it on multiple different major websites over the past couple of months and not noticed it from other locations where I don't use Three Broadband so does seem to be related to the router/connection (this is via wired Ethernet too, so not a WiFi problem).  I've tried changing DNS server in case that helps but no difference.

It mainly seems to happen when trying to first load a site or (annoyingly) at checkout when a different site is being loaded as part of the checkout process.  It certainly doesn't happen everytime but does happen with reasonable frequency.  I've also noticed I often get it when trying to pull/push from/to Github too and have to do so a number of times for it to work (browsing the Github website works fine).

I'm using a NR5103E with Firmware Version V1.00(ACBJ.0)b14 - I tried rebooting it but to no effect.

[bytespider]

Even 7 hours later adult material still can be accessed, so that toggle does nothing.

[Midnight54]

IIRC when I first got my router,it took either 24 or 48hours from requesting it to being able to access your favourite content 🙂

[bytespider]

My favourite content 🤣

I don't think they should have any restriction at the ISP level it should be something at the router level. Like Eero, Adguard, and PiHole. But we digress.

[bytespider]

😂Geez! In this case the appear to have an invalid certificate on the support domain.

❯ ./checkssl.sh 'https://support.three.co.uk'
---
Testing: https://support.three.co.uk
---
Attempt 01: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 02: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 03: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 04: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 05: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 06: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 07: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 08: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 09: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 10: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 11: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 12: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 13: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 14: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 15: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 16: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 17: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 18: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 19: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
Attempt 20: Error - SSL: no alternative certificate subject name matches target host name 'support.three.co.uk'
---
SSL Errors: 20/20
---

[AkiTaiyo]

Different SSL error to the connection dropped one..
This one is due to the certificate being returned from this URL, not being valid for the URL..

[bytespider]

oh I'm aware I just thought it was funny, since we're talking about connection issues

[AkiTaiyo]

Cant find any link from three main page that links to this url anymore, so presumably they have dropped it..

[bytespider]

It's linked from the account plan page

[Midnight54]

Currently the most commented on thread in this forum section, but the lack of much response from Three or at least transparency on what they're doing to resolve the problem with regular updates is unreal....this must be affecting many many people.....of course some will blame alsorts, such as signal, websites, wifi, phone etc but this fault definitely lies with Three, and it seems to come and go with severity at random (currently not too bad but its still there).  Do no Three engineers use their own broadband provider?

[AkiTaiyo]

If anyone is interested, I've made my app+source available. 
It's hacked together in C# so feel free to make improvements on it.  Requires .net8 to run the binary.  Tries to categorize most of the errors (in a really dodgy way).
Gives you a readout like this on the console window, press "esc" to stop it running, but it doesn't save the results so you will want to copy/paste them to somewhere before closing the window!

Source + binary in zip format from my Google Drive.  See the 'bin' folder for the pre-built binary.
https://drive.google.com/file/d/1xMaD4DJEGjJFUASdMI0ARnibB39Zru4H/view?usp=sharing

urls.txt file controls the sites it requests.  Don't include the https://
Feel free to use + make changes, publish to github or whatever..