Last August openreach relocated my PCP. In June I changed ISPs and during transition my PPP connection was down for 18 hours (because I hadn't noticed and forgot to change the credentials when I left for work). Up till that point I'd had a solid 67Mb/s according to speed testers for a couple of years but after changing ISPs I only got 55Mb/s. Over the following months I had a couple of early morning drops but nothing much changed.
This weekend I decided to set myself up to backup a large amount of data to the cloud. About forty minutes into the upload (while I was out) my line lost sync and my HG612 failed to reacquire it (or couldn't be bothered). So when I got home I had to power cycle the modem.
I'm now back to a 67Mb/s throughput. I mentioned this to a friend and they reminded me that they had a similar experience. A long period of poor sync speed apparently 'cured' by sending large amounts of data upstream.
Is this a coincidence? My line is normally completely stable so having the line drop in the middle of the afternoon is rare. I'm just wondering if, maybe, the upload traffic caused the DLM to re-assess my line and restore my original sync speed. For what it's worth although my downstream dropped with the change of ISP my upload appeared as good as ever at around 18.5Mb/s.
Sadly I don't currently have an unlocked modem so can't provide stats.