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Struggling with frequent SYNC loss and customer support making me jump through hoops

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My setup is that I use a VM Hub 3 in Modem Mode, with my own wireless router connected to it that provides our main home network.  We have had no issues for more than 2 years, and the more advanced setup suits us because our home network is quite complicated with wireless speakers, IOT devices, home assistant setup and so on.

In the last few weeks we've started to get frequent WAN drop-outs that seem to occur several times each day for up to 30 seconds at a time.  Internal wifi was fine, I checked our router logs and ultimately traced it to the VM Hub itself.

Via the Hub's network tools / logs, I have uncovered what appears to be a frequent loss of synchronisation - I'll post the full output (log, downstream, upstream, etc.) but we get this 5-6 times per day:


criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;

From my perspective, this absolutely correlates with what's been going on.  We've had a lot of building work around here recently, plus lorries are always reversing into the grey on-street cabinets so it wouldn't surprise me if there is an issue with line noise or connectivity.

From my perspective, that should be enough to get a technician to visit and examine the street cabling, fibre box etc.

But, on the phone, customer support are now insisting that I re-enable Router mode on the hub, turn off our own router completely, and run a 48 hour 'experiment' to rule out what I presume is issues with our router, etc.  This is pretty disruptive.

It also feels a little pointless. Why am I having to jump through these hoops, have I missed something here or are the critical log entries in the Hub not sufficient evidence that we need somebody to check the on-street connection to the cabinet?  Is there no other way?

I actually work in an I.T. company but of course I also acknowledge I'm no expert in DOCSIS, fibre, etc. so I don't want to sound arrogant - hence the community post to canvas opinion on this!


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My Broadband Ping - My VM Internet Connection

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Very Insightful Person

That's not a great start for a BQM.  Should get a better picture after 24 Hours.

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Tuning in

Nearly at the end of the 48 hour 'test' and we had another 2 days of frequent loss of Internet connectivity, between 20-30 times per day.


My Broadband Ping - My VM Internet Connection


All it has done is seem to confirm what I knew already - the problem is not on our side of the Hub. 

I really hope I can get the phone support person to agree to send out an engineer now, we can't go on like this!

Hi @carlosp_uk 👋 Thank you for your posts and welcome to the Virgin Media Community 😀

We're sorry to hear about the problem you've been experiencing 😔

In order to discuss this with you further, we'll send you a private message on here. Look out for the envelope in the top right-hand corner.


If you're on a portable device with a smaller screen, click on the icon in the top right-hand corner and select "messages" from the additional menu options.

Thank you for your support @Adduxi and @Client62 👍