18 months of issues

My dad has continual problems with his broadband which has been going on for ages now, the connection can sometimes be fine for a few days, and then suddenly becomes very unstable and stuggles to maintain a connection, after numberous calls to the ISP and engineer visits, they cannot find any faults but the issue persists.

They cannot replace the copper because it isnt ducted, it would involve digging up the trench all the way from the house to the street side cabinet.

What can be done? It was the same when he was on ADSL2+, he switched to VDSL in the hopes it would be more tolerant but doesn't seem to have been the same, it seems to be steadily getting worse.

Installing full fibre?

VDSL2 is less tolerant but for many is better due to the shorter distance of metal wiring used.

A lot hinges on what the connection speed, attenuation and noise margin figures are and what would be expected for the distance involved, i.e. it may be the line could be more stable if some speed was sacrificed and the DLM system usually does this for people.

Another issue is that VDSL2 modems can vary a lot in how they behave so what router is attached to the line?

Full fibre is somewhat cost prohibative.

Happens with both the Plusnet supplied modem and a Fritzbox! modem. Even with all the tweaks on the fritzbox turned right down to the lowest ( most stable).

Which plusnet modem they have used many over the years.

Its a long shot but sticking something like a Zyxel VMG1312-B10D between plusnet and line with Zyxel running in bridge mode and connected to WAN port of the plusnet might help.

Any ideas on the stats?

I don't have access to the stats at the moment but it syncs somewhere around 30-40mbps