Been having similar issues. I had a standard adsl service 15Mbps/1Mbps and reasonable ping of 20ms to bbc.co.uk, but it would drop out 3 or 4 times a day. Running the BT Speedtest appeared to have found a fault and created a ticket back in May, and Openreach dutifully came out, sprinkled pixie dust and problem (I never saw it) went away. A month ago the same problem occurred (speedtest generates a ticket) and OR were again sent to investigate and concluded it was a faulty card on the ISP (BT) side, so a lift and shift was requested and done. I immediately lost about 30% of my throughput, and when I queried this I was told a) its because I use wifi - no, I am directly connected to BTHomeHub, b) because I use too many devices - I dont, I disconnect everything except my PC when testing, c) I should test using BT Wholesale tester - I do, and get a worse result than the old dos ping!
PingPlotter and TRACERT both showed an issue in the exchange somewhere, so another OR engineer (number 3) was sent who found some new error on the line and shifted me to a new twisted pair, which tested 99% clear, and BT did some magic on the ISP equipment. Sadly the same thing happened and I am now down to frequently experiencing >2000ms and when that happens the line speed drops below 0degK so the service has pretty much deteriorated to unusable, which is forcing me to have to abandon working from home and risking my health by going back into the office.
I also dont have the luxury of fibre, because Virgin own the rights in my area and want mega £ to lay 30m of fibre from the nearest access point.
So after 17 years of using BT at home and in my businesses, I am now looking for a company who actually cares.
And yes, as was pointed out to me during one particularly condescending call from BT, I know an ADSL line is on guaranteed to 2M/500K s o anything above that is gratis. The problem appears to be in BT's ISP equipment but there is no appetite to spend money on maintaining or making it fit for purpose at our local exchange.
PS I dropped IPv6 from my PC, no change
