Although I'm currently using the FB 7490, my connection apparently re-synced this morning though I have no idea why. Looks like DLM intervention as there was no error spike, yet everything is the same as it was. No G.INP change, no SRA change, no interleaving applied, no increase or decrease in maximum sync rate. Very odd, I wonder if BT is rolling out a new set of DLM profiles to ECi cabs?
DLM system typically does that to my connection every couple or so weeks. Most of the time nothing changes. I know (or am pretty sure) why it does it (on an ECI openreach modem setup with homehub 3 or 4 at least).
The ECI modem will often have a change of profile but the homehub will not recognise fully a change has taken place so the connection speed remains performing as it was until you either manually reboot the homehub or let DLM intervene again to do it.
A good example is up until recently i was DLM'd which always reduces my connection down to 64-68(ish)Mb and ping to the bbc basically doubles to around 20ms. My connection speed is normally (IE no DLM intervention) in or around the 70-76Mb throughput range without DLM and ping to the BBC is around 10ms.
I always know when DLM has relented as although the connection speed can get stuck at the 64-68Mb the ping time will go back to the 10ms range.
A quick reboot of the homehub ONLY and the speed then goes back up to the 70-76Mb range.
Basically i think sometimes the router part (at least in the homehub 3 and 4 case) does not restart/resyn with the modem. So DLM does it instead every couple of weeks if a number of profile changes in that time have taken place.
Its not always the case sometimes you can get DLM'd or have DLM removed and the hub will also restart/sync with the modem, but sometimes it does not.