Must be a similar thing we are experiencing
Gigafast 900/900 Pro via cityfibre installed March flawless serivce 900+ up and down all day and night.
Since beginning of August looking at my thinkbroadband BQM I suffer horrendous packet loss between 4pm to midnight progressively getting worse (to the point I finally noticed) late august and september is even worse.
Download speeds can be as low as 50mb in an evening (upload maintains the 900mb+), however if I use a VPN and route myself even to america can get 600mb+ so clearly network congestion somewhere.
Vodafone have been moving me around (and say they have with lots of folk) to try and balance the load admitting their is a congestion problem but the 'fix' of a better connection keeps being pushed back and now support flat ignore my enquiry for an update.
Don't hold out much hope tbh this is the same support that made me do my tests again because I only showed the wifi disconnected why they would think I would do a speedtest while other devices were connected is beyond me, I took someones advise about replacing their kit with your own and tbh the speeds (lack of) are still the same.
