Hi, For the record, I am on FTTC and approximately 1800m from the cabinet with the wired element being copper partly underground and partly overhead and currently using the Plusnet Hub One router.
After months of persistence Open Reach have finally repaired the core fault in the underground part of the copper line (a roadside drain pipe had bust and flooded a connector). Prior to this final repair I was having lots of dropouts and speeds of around 6Mbps. Tests on the line after the repair, at the Master Socket, showed 22Mbps at the socket before the VDSL filter and 20Mbps at the DSL plug into the router. Following that test the line was capped by Open Reach) and they told me that they would cap it at 16Mbps. Accessing the Hub Manager it seems that it was capped at 13Mbps. Wired tests at the PC after that showed a consistent 11.5Mbps (still below the contracted minimum) and after 8 days of uninterrupted service at that level I decided to replace the Hub One router with a BT Smart Hub 6 that I had waiting in the wings.
No problems setting up the route, thanks to guidance on this Forum, but after installing line speeds dropped to 7.5Mbps. I had expected DLM to drop but not by that much. I left the BT router in place for 48 hrs expecting to see firmware updates and speed improvements but neither expectation was met. No firmware update and speed still 7.5Mbps
For unconnected reasons I then restored the Plus Net router and speeds remain at 7.5Mbps after a further 72hrs. I spoke to customer services yesterday to try and get the cap lifted and it was agreed that, having a stable platform now for 2 weeks there was no further reason for the cap and that has been referred to the Faults Team to adjust.
However, I wondered how long it should take, if the line is stable, for DLM to adjust the speeds back to the capped levels after my intrusion into the line by changing routers? It seems a bit like the reverse of fuel prices, drops quickly and and recovers very slowly.