Loss of sync when phone is answered

[#1]

If you get a new router then consider getting one which will work with your monitoring program. The fact that the sync does not drop with a specific router which you cannot monitor, does not mean the problem has been resolved ... it just might mean you have a router which is more tolerant of the fault.

Is there any phone extension wiring present here? The bell wire being connected on extension wiring (regardless of any phones being connected to it) can be unhelpful. Having replaced the user end filters ... a faulty line card in the exchange can cause this exact fault.

[#2]

Thanks to everyone for your thoughts.  Have fitted a new faceplate filter (AdslNation) have disconnected the one extension and have also got the phone double filtered with a microfilter in the faceplate.  No more loss of sync nor any change in the snrm when the phone rings/used however still getting a burst of CRC errors upstream when the phone rings up from 0 to 18 per minute (no SES errors). Appears DLM has increased upstream margin to 10.

 I now think my problem has been going on for some time. I was connecting via a Dlink DSL 2740B for some years.  I kept losing sync at random intervals for no reason and it would not resync, so I got a second hand Archer D5.  That's when the real problems began I was soon banded at around than 1MB, as the router could not hold sync, with many many drops a day. I did not link this to the phone as I had no way to monitor the stats.  Enter a Billion 7800DXL off ebay and dslstats. I then noticed the problem.  

I have dealt with filters and extensions and made progress.  The Dlink is compatible with dslstats so will see if the spike in errors is present when using it. 

[#3]

What type of connection are you on? Reason I ask is there is a known problem with certain exchanges and Max Premium (ADSL1 8128/832) that exhibits exactly the symptoms you are describing.

[#4]

As far as I know I we are on 21CN.  How can I tell? Router  reports ADSL2.

[#5]

It's not that issue then.

[#6]

Hello @melindwr

We are wondering how your connection is looking and if the problem is still persisting? Please get back to us if you still need any assistance.

[#7]

This sounds like a reapeat of a problem that I and other users suffered some years ago. After many visits from BT  OR engineers , Eventually a very persistent Openreach engineer who refused to accept defeat contacted the BT research centre who supplied the cause and the fix. There is a known incompatibility between the System X telephone system and older Ferranti Mk 1 ADSL BROADBAND equipment.  

Heres a link to the relevant discussion https://community.plus.net/t5/Broadband/ADSL-Loses-Sync-on-Incoming-Calls-But-NOT-a-noisy-line/td-p/...