Gradually slowing Fibre speed

I joined Plusnet in January. My estimated sync was c. 26 down so I was thrilled to see 33 down when the service started. This fell over the first week or so but settled at almost 30 down and 7.5 up so I remained happy. This was consistent (outside of some of the issues lots of Plusnet customers seem to have suffered with high pings and low speeds some evenings).

Then around 10 days ago my speed fell down to around 27 down but the up speed went up to 8.5, where they've both stayed since.

Is this usual ? I've avoided re-setting my router and modem because I'm unsure of the impact of re-starting the modem (unlike ADSL etc where it doesn't seem to cause any issues). Did anything change generally in late March that might have affected the speeds, or should I report the fall ? I'm aware that my speed is pretty much now where the original estimate was, but it held the higher speed for almost 3 months.

Thanks

There could have been some incident that caused it, and a simple turn off of the modem, then back on after a minute wait should cure that. I recommend doing that inside daylight hours. Don't do it many times!

It might be better also to turn off the router, and turn that back on after the modem has connected. It is possible for routers to get confused or clogged up as well when out-of-the-ordinary events occur.

Another possibility is that over the time you have been on FTTC there have been several more connections to your cabinet, and the latest one was the straw that broke the camel's back. It is quite common for later connections to cause cross-talk with earlier ones, and once that reaches a certain level, (like noise on ADSLx), there has to be a lower speed re-sync. There's nothing you can do about that, but there is something called Vectoring being looked into by Openreach. That's a system to cancel out cross-talk.

The third possibility is similar to the cross-talk one above, where error rates on the line have caused interleaving to be turned on. On FTTC that reduces the sync speed. If the noise was temporary then several posters have reported it being removed after a couple of weeks or so.

There is a sort of consensus that the pre-connection estimates on the BT Wholesale site take account of forecast cross-talk.

Thanks for the response. I re-set both the modem and router early this morning and the speed HAS gone back to what I was getting prior to 10 days ago so hopefully it was just a reset that re-sync'd at a bad time (does that apply to fibre lines ? Presumably it can with FTTC as there's still a copper element in the line and mine is about 500m apparently.

Thanks