PPP connection drops and won't reconnect without router reboot

[#1]

I've been having this ongoing problem now for months, and seem to have run out of options.
When I my router connects up to the internet, everything is fine sometimes for a few hours, sometimes only for a few minutes.
When it fails, if I check the Diagnostics on my D-Link router, it shows a failure to say that it can't ping the DNS server (hence why I can't surf anymore) and can't ping the ISP default gateway (i.e. can't see PlusNet, I guess).  Eventually it will fail on the other checks for PPP.  On the syslog I can see it's trying to start up the PPP session again, but is never able to.  The only way I can get things back is via a router reboot.  I am and have been plugged directly into the BT Test Socket for sometime.
BT have now been out twice.  First time they change the NTE socket, as it was quite old but the problem didn't go away (typically happened 20 mins after the BT engineer left).  They came back again yesterday and did the same tests, and the ADSL sync is fine, which I have seen through all my monitoring - it never seems to drop with no errors.
So the problem I definately have is at the PPP layer and why it is disconnecting.  PlusNet have provided some logs from their end on my fault ticket, which show some user initiated resets, which will be when I reboot, due to DNS/Default Gateway failure, but it also showed some terminations from their end, which to me, says that's the full PPP failure - I could be wrong.
If anyone needs specific router/setup information, or wants me to post any of the info on my fault ticket let me know - any help at this point gratefully received.

[#2]

This is the same as my problem!
http://community.plus.net/forum/index.php/topic,78341.0.html
I spoke to link:csa removed yesterday (PN Tech) who said that he had come across this before and that it's definitely down to BT, probably in the exchange or on the backhaul. The significant thing is that we aren't losing DSL sync. It might be worth you using the DMT Tool to prove that DSL stays up when the PPP is lost with the same connection speed showing after the event.
http://www.kitz.co.uk/routers/DMTv8.htm
adie:blue CSA removed as per link:rules mod:end

[#3]

Hi,
Thanks for confirming this - there's a slight bit of comfort knowing I'm not the only one suffering this problem and hopefully there is a fix, if someone gets their finger out and sorts it.
I've installed this software and it is monitoring my router and the DSL link etc.  Does this monitor PPP as well, as I can't see that anywhere, or do I have to supply logs from this software and then syslogs from my router to prove the ADSL is still synched and all okay after the loss of PPP.
Thanks again for your help.
Paul

[#4]

No it doesn't monitor PPP as such. Plusnet will be able to tell you what times your sessions start and end though and you can see from your DMT graph whether you lost the DSL. According to my DMT I've been connected for more than three days continuously but according to PN I was offline from around 11am Thursday to 3pm-ish Friday (while I was away)..  and that was caused by loss of authentication.

[#5]

Glad to report my problem has finally been fixed.  PN arranged for BT to come out for a 3rd time, and the morning of the appointment, I got a call from the BT Openreach engineer saying he was at the Exchange and wanted to move my line onto a different and new piece of broadband kit - so he did this, and everything came up okay and he said we'd have to monitor it.
2 weeks later my connection is completely solid and I have closed the case with PN.  So if you have a similar problem, then it does seem to be a BT problem in the Exchange and I would push extremely hard to be move to a different connection point in the Exchange.
Hope this helps - and good luck!

[#6]

Hi Paul.
Glad to hear that your problem has been fixed.

[#7]

Hi Paul,
I also had a so-called lift-and-shift done in the exchange - fresh DSLAM and changed routing - unfortunately didn't make any difference to the PPP drop problem but it did result in a much "cleaner" connection (as shown by the routers data error log). But I agree it's certainly a BT problem. I'm now happily sailing along using PPPoE with no problems whatsoever (been connected for nine days solid).
EDIT: took four visits from BT to achieve the L&S.