Frequent and random dropped internet connections on TG585 v8

[#1]

This has been happening frequently and randomly for about three weeks now.  The day before yesterday I had a few of these while yesterday there were none but today it's happening very often.  The router details are as follows and it is connected to the master phone socket and I've tested the line for noise and there is no issue there.  I hardly use the land line so this is not connected to the phone either.  I've tried rebooting the router as well but to no avail.  Whenever the internet connection is dropped I get a "xDSL linestate down" error as shown in the router event logs below. 
When the problem happens the internet light on the router disappears for a couple of minutes and then comes back as red followed by green once the connection is restored.  The first four lights on the router remain green.  The connection is usually down for about 3 minutes.  Any ideas anyone?  Is this a router issue?

Router: TG585 v8
Event logs are as follows:
Jun 28 22:18:37 FIREWALL replay check (1 of 8): Protocol: ICMP Src ip: 220.78.182.58 Dst ip: 195.166.151.89 Type: Destination Unreachable Code: Port Unreacheable

Jun 28 22:17:24 FIREWALL event (1 of 1): deleted rules

Jun 28 22:17:20 PPP link up (Internet) [195.166.151.89]

Jun 28 22:17:20 GRP Default destination is routed via gateway 195.166.151.89

Jun 28 22:17:20 PPP CHAP Chap receive success : authentication ok

Jun 28 22:17:18 PPP CHAP Receive challenge (rhost = pcl-ag06)

Jun 28 22:17:12 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 28 22:17:11 xDSL linestate up (ITU-T G.992.5; downstream: 9727 kbit/s, upstream: 444 kbit/s; output Power Down: 18.0 dBm, Up: 12.0 dBm; line Attenuation Down: 23.5 dB, Up: 12.5 dB; snr Margin Down: 11.5 dB, Up: 27.5 dB)

Jun 28 22:16:52 PPP link down (Internet) [195.166.151.89]

Jun 28 22:16:45 xDSL linestate down

Jun 28 22:16:22 FIREWALL event (1 of 1): created rules

Jun 28 22:16:21 GRP Default destination is not routed anymore via gateway 195.166.151.89

Jun 28 22:16:21 xDSL linestate down

Jun 28 22:15:58 FIREWALL event (1 of 1): deleted rules

Jun 28 22:15:55 PPP link up (Internet) [195.166.151.89]

Jun 28 22:15:54 GRP Default destination is routed via gateway 195.166.151.89

Jun 28 22:15:54 PPP CHAP Chap receive success : authentication ok

Jun 28 22:15:52 PPP CHAP Receive challenge (rhost = PTN-AG03)

Jun 28 22:15:52 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 28 22:15:49 xDSL linestate up (ITU-T G.992.5; downstream: 9727 kbit/s, upstream: 444 kbit/s; output Power Down: 19.0 dBm, Up: 12.0 dBm; line Attenuation Down: 23.5 dB, Up: 12.5 dB; snr Margin Down: 6.5 dB, Up: 27.0 dB)

Jun 28 22:15:26 PPP link down (Internet) [195.166.151.89]

Jun 28 22:15:23 xDSL linestate down

Jun 28 22:14:59 FIREWALL event (1 of 1): created rules

Jun 28 22:14:58 GRP Default destination is not routed anymore via gateway 195.166.151.89

Jun 28 22:14:58 xDSL linestate down

Jun 28 22:13:53 FIREWALL replay check (1 of 4): Protocol: ICMP Src ip: 220.78.182.58 Dst ip: 195.166.151.89 Type: Destination Unreachable Code: Port Unreacheable

Jun 28 22:12:48 FIREWALL event (1 of 1): deleted rules

Jun 28 22:12:44 PPP link up (Internet) [195.166.151.89]

Jun 28 22:12:44 GRP Default destination is routed via gateway 195.166.151.89

Jun 28 22:12:44 PPP CHAP Chap receive success : authentication ok

Jun 28 22:12:43 PPP CHAP Receive challenge (rhost = pcl-ag04)

Jun 28 22:12:39 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 28 22:12:37 xDSL linestate up (ITU-T G.992.5; downstream: 9727 kbit/s, upstream: 444 kbit/s; output Power Down: 18.0 dBm, Up: 12.5 dBm; line Attenuation Down: 23.5 dB, Up: 12.5 dB; snr Margin Down: 12.0 dB, Up: 27.5 dB)

Jun 28 22:12:22 PPP link down (Internet) [195.166.151.89]

Jun 28 22:12:12 xDSL linestate down

Jun 28 22:11:49 FIREWALL event (1 of 1): created rules

Jun 28 22:11:48 GRP Default destination is not routed anymore via gateway 195.166.151.89

[#2]

It could be a router problem or potentially a fault on the line. It looks like the DLM has put you on a banded profile, presumably due to the frequent connection drops. When the connection drops sync is being lost with the exchange so I would expect the broadband light also to go out, then flash and finally return to steady green. Activity on the internet light should follow as the PPP session to Plusnet is re-established.
You could try resetting the router to factory defaults (which will require your broadband username and password to be re-entered - the router will do that itself if easy start is configured).
If the problem continues.do you have a spare router to try? You need to verify whether that eliminates the dropping connection problem.

[#3]

Thanks spraxyt for your response.
I will take on board your suggestion about resetting TG585 v8 router back to factory settings.  Also, I'm thinking of ordering the following router.  Any idea whether it's any good?
                          TP-Link TD-W8960N 300MBPS Wireless N ADSL2+ Modem Router for BT connections
http://www.amazon.co.uk/TP-Link-TD-W8960N-300MBPS-Wireless-connections/dp/B0031SUB4S/ref=wl_it_dp_o_...
I left the router powered down overnight and within 15 minutes of turning it back on this morning it started happening again.  I stream music using sonos so very aware of connection drops.  The connection specific event log is as follows:
When this happens broadband light first blinks while the internet light goes off.  Internet light then comes back on as red while the broadband light stops blinking and soon after the internet light turns green.  The whole disconnect reconnect process usually takes less than two minutes but occasionally can take longer. 
There have been no interruptions for 40 minutes now and the connection specific event log from this morning is as follows:
Event Logging
This page summarizes the last events that have been recorded on your Thomson Gateway. Choose a display filter...

Category:
Recorded Events

Time Message

Jun 29 09:54:58 PPP link up (Internet) [195.166.151.89]

Jun 29 09:54:58 PPP CHAP Chap receive success : authentication ok

Jun 29 09:54:57 PPP CHAP Receive challenge (rhost = pcl-ag05)

Jun 29 09:54:54 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 29 09:48:53 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 29 09:48:39 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 29 09:48:34 xDSL linestate up (ITU-T G.992.5; downstream: 8372 kbit/s, upstream: 444 kbit/s; output Power Down: 20.0 dBm, Up: 11.5 dBm; line Attenuation Down: 23.5 dB, Up: 12.5 dB; snr Margin Down: 6.5 dB, Up: 26.5 dB)

Jun 29 09:48:14 PPP link down (Internet) [195.166.151.89]

Jun 29 09:48:08 xDSL linestate down

Jun 29 09:47:43 xDSL linestate down

Jun 29 09:46:54 PPP link up (Internet) [195.166.151.89]

Jun 29 09:46:54 PPP CHAP Chap receive success : authentication ok

Jun 29 09:46:54 PPP CHAP Receive challenge (rhost = PTN-AG04)

Jun 29 09:46:53 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)

Jun 29 09:46:47 xDSL linestate up (ITU-T G.992.5; downstream: 9727 kbit/s, upstream: 444 kbit/s; output Power Down: 18.0 dBm, Up: 12.0 dBm; line Attenuation Down: 23.5 dB, Up: 12.5 dB; snr Margin Down: 1.5 dB, Up: 29.5 dB)

Jun 29 09:46:11 xDSL linestate down

Jun 29 09:45:47 xDSL linestate down

Jun 29 09:45:24 xDSL linestate up (ITU-T G.992.5; downstream: 9727 kbit/s, upstream: 444 kbit/s; output Power Down: 18.0 dBm, Up: 12.0 dBm; line Attenuation Down: 23.5 dB, Up: 12.5 dB; snr Margin Down: 13.0 dB, Up: 28.0 dB)

Jun 29 09:45:10 PPP link down (Internet) [195.166.151.89]

Jun 29 09:44:59 xDSL linestate down

[#4]

Sorry, I'm not familiar with the TP-link range of router-modems so comment on those will have to come from others.
The behaviour of the broadband and internet lights on the router when sync is lost is what I'd expect. So that's OK.
However the re-syncs this morning that you posted show odd behaviour, SNR margin-down initially 13.0dB, then re-sync a minute later 1.5dB, and re-sync again 2 minutes later 6.5dB at a sync speed reduced by 1350kbps.
Something is seriously amiss. Have you tried a different filter? Should have asked that last night.
I'd suggest raising a dropping connection fault at http://faults.plus.net to get this looked at officially. That includes a set of diagnostic checks.

[#5]

Thanks spraxyt.  Wonder whether anyone else is using that router.
I changed the filter as suggested by PlusNet a couple of days ago and it made no difference.  I've raised a ticket with Plusnet and they are testing my line.
All this started happening around the 10th of June give or take a few days.  Before that it was not as frequent.  I've been streaming radio and no drops today so far though.

[#6]

dumb question time
have you tried listening on the phone line during the dropout's to see if there is any clicking or static hiss ?
have you tried running a quiet line test (17070) to see if there is any noise in the line (especially during a dropout cycle)
it seems from your log that instead of allowing connection at 6bd and then dragging (adjusting up or down) to a stable point it is forcing a resync at various db's to find the best one each time (which is very strange) although I don't understand if that's a banded profile issue and intentional or an oddity of the tplink stuff
the sync speeds are similarly all over the place with each db change although perhaps that's to be expected as line quality is improving or decreasing and your in a banded profile changing bands (although normally as I understand it the point of banding is to force a particular band onto a connection at the dslam to create greater stability)
either way if you can get another router and use it to test the connection over a 48hour period it would certainly help to eliminate that as being a problem

[#7]

Thanks nanotm.  Have tried quiet line test via 17070 and that's fine.  The music has been streaming non-stop since morning and I'm going to leave it streaming all night as well.  Sonos (ZP80) does not restart streaming automatically if connection is dropped.  Plus net are running a line check and will update me in 48 hours.

[#8]

Our faults team are currently checking over your connection, they'll update you as soon as they can.
Let us know how you go on.

[#9]

Thanks chrispurvey.  The connection has been up with no interruptions for 24 hours now. The fault team told me that they will get back to me with feedback and will close the call after that.

[#10]

I've been streaming radio via sonos for about 48 hours now and it looks like the connection was dropped just once, last night.  The connection specific event log is:
Category:
Recorded Events

Time Message

Jul 2 03:22:22 PPP link up (Internet) [195.166.151.89]

Jul 2 03:22:22 PPP CHAP Chap receive success : authentication ok

Jul 2 03:22:21 PPP CHAP Receive challenge (rhost = pcl-ag08)

Jul 2 03:22:20 PPP CHAP Receive challenge (rhost = bras-red7.l-wat)


Just had this from PlusNet:

We have asked our wholesale broadband suppliers to turn interleaving on on your phone line to try and fix your current broadband problem.
Interleaving is a form of error correction that helps to improve the stability of high-speed broadband. One drawback of interleaving is that it can increase ping times, which may cause problems for online gamers.
We think that turning on interleaving may help with your connection problems. Interleaving usually takes 24 hours to turn on, but can take up to 5 days to take effect.
If you are still seeing problems with interleaving switched on please get back in touch with us. Thank you for your time and patience

Kind regards,
Plusnet Customer Support
http://www.plus.net/
Hopefully, this should fix all this.  Thanks everyone.