Speed decreased - BT unsure why

Hi

Just wondering if there's any reason that my line speed on BT would drop from (this taken from the HH6) 60 Mbps download\20 Mbps upload to 49 Mbps download\16 Mbps upload


For roughly 22/23 months I was getting a steady 54-56 Mbps download\17-18 Mbps upload when doing a speed test but now getting 43-45 Mbps download\ 14-15 Mbps upload, has been happening for the last 5 weeks and before that the HH6 had been on for about 4 weeks straight before it went off randomly at 3am one night (thank BQM for the exact date and time)

Have tried to get this resolved with BT with one agent saying it was due to a cap being put on the line then when I made a complaint about another agent promising me that if I waited 20 minutes after the call, then turned the modem off for 30 seconds then back on, he'd guarantee that the speed would be back to normal, I was told that these thing happen and as I'm above the 'Minimum Guaranteed Speed of 38.1 Mbps' they aren't going to look into.

Reason I'm also asking is that my contract is up in a few weeks time and am planning to go elsewhere, and I don't want it effecting that service as well.

Could be increased cross talk as more people use the service and the signals interfere with each other.

Could be the dynamic line management has seen errors/instability and slowed you down to improve things, power cuts or low voltage events in an area tend not to help with this, as will thunder storms.

Could be they've tweaked the firmware and the new firmware is not as efficient at populating the VDSL2 spectrum and giving slightly lower speeds. If this was the case given the vast majority use the HomeHubs we would see a drop across the speed test population.