Try the 3.8.2.2_STD as that has been stable on my line. Raise a ticket also with support to as it may help to get this sorted. You can downgrade to 3.8.x software but I don't think you can downgrade below that and keep your configuration. I believe the magic numbers are normal, I have seen them in my syslog, are you seeing PPP disconnects and reconnects in your syslog?

Having the same issue with the same settings/firmware as Matt. PlusNet ISP.

The 2860 disconnects so regularly that the IP profile of the line is reduced, which doesn't actually help the connection at all. Tried a complete reset, but no help. Got a load of Magic Number entries in syslog as Matt describes.

I am assuming you have tried installing the version of 3.8.2.2 with the default modem code? G.inf hasn't been implement right across the BT estate yet, so defo worth a try.

Yes this is after trying 3.8.2.2 with default modem code. I also tried the second modem code on the firmware.

Just as an extra note, I've just tried downgrading to 3.8.1 and so far had two disconnects in 10 minutes.

Keen to hear what others have tried.

Stayed stable for about 12 hours, then is up and down every hour or so. Each time it connects at varying speeds.

Tried disconnecting everythin else connected to the phone line, to no avail as yet.

Be interested to hear others solutions, presuming we're not the only ones.

Should we try a new router?

My line had similar issues, the VTx builds of 3.8.2.2 produced the same instability, I am currently using 3.8.2.2_STD 548006 (on a 2860ac) and we have been stable for a couple of weeks now. We also had the issue that the line profile started to drop, because of this so we reverted back to the openreach supplied modem on WAN2 to get our profile back up. It is worth raising a support ticket and also when posting in the forum including the full modem version for clarity of what you have tried, Draytek support have a copy of my router config and are investigating, I am sure that having more information they will get to the bottom of this issue.