I recommend contacting support for assistance - it might be possible to solve the problem you're seeing with different modem codes or firmware. Do you know if any characteristics of the line have changed since the problem began? The SNR value and speeds look normal, but the error shows it's dropped because the remote side terminated?

Try the Vector 4 modem code to see if that helps, but I think giving logs to the support team might be the best way to get a fix for this.

Thanks for that excellent advice.

With the Vector 4 code, the connection has been up for 24h30m so far. Keeping my fingers crossed.
I do note the log says:
<166>Jan 1 00:00:26 DrayTek: [DSL] G.Vectoring Status: OFF

AAMOI, if vectoring is off, why would it make any difference which vectoring mode was built in to the code?

If changing the vectoring has improved stability over the _BT version, does that indicate what sort of problem there is?

And why would the BT OR modem be completely stable?

Apologies for the barrage of questions - just interested in understanding the underlying problem.

It's unlilkely that you have vectoring enabled on your line, there's very few cabinets with it enabled. With your OR modem you could check the vectoring state by telnet with the command xdslcmd info --vectoring.

Despite your line being stable for years it could still have developed a fault somewhere or with a large uptake in connections from your neighbours you could be seeing increased levels of crosstalk which would adversely affect your SNRM causing the disconnects and your OR modem, with the Broadcom chipset, has proven stability with Huawei DSLAM equipment.

There's a chance that your connection drops will come back unfortunately, in which case, if you haven't already, I would google "HG612 unlock" and look to use the software DSLstats to get minute by minute monitoring of your line stats and a picture of the crosstalk on your line

I'm sure you're correct as the log says Vectoring: OFF.

I'm still puzzled as to why the V4 (presumabling falling back to no vectoring) works so well when V2/V3 (which must also be falling back to no vectoring), fails to maintain the connection.

The Vector4 firmware (but vectoring:OFF) has now been up for 80 hours.
Thanks for the pointers to unlock the BT modem. I'll do that if/when I need to.

Just stumbled across this thread while looking for possible solutions for an identical problem on BT VDSL. My 2860 has been dropping out periodically since around June, but became very bad on Christmas Day (coincidence?). BT have been chasing this since early January, and 4 call outs later they have
[*]replaced faulty cable to the house
[*]changed faulty cable to the manhole
[*]checked the line multiple times

Each time, the problem went away and came back. The line tests are now near perfect, apparently.

Most interesting was the latest engineer, who asked if we still had Christmas lights up - a bit of a random question. Apparently he had been having a few issues with REIN from cheap lights. Powered everything down, and all the errors his kit was detecting went away. Not the end of the story though - powered everything up, and still no errors, and a line testing near perfectly. Sure enough the problem is back, although I *did* find the router power supply was dodgy (giving out large amounts of electrical noise at 612kHz, classic REIN)

I am now tearing my hair out trying to work out if it’s my end, or BT! We are now experiencing disconnects every 5-10 minutes.

Quick update: just changed firmware to Vector 4, and the CRC count (and other error counts) are all zero. I was getting hundreds of CRCs per minute with the _BT firmware.

Only been running for 10 minutes, but having zero errors so far is a hugely encouraging sign.