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

[carlosp_uk]

Hi

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:

critical	SYNC 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!

[carlosp_uk]

Downstream bonded channels

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID

1	138750000	3	36	256 qam	1
2	146750000	2.9	36	256 qam	2
3	154750000	3.2	37	256 qam	3
4	162750000	2.9	38	256 qam	4
5	170750000	3.2	38	256 qam	5
6	178750000	3	38	256 qam	6
7	186750000	3.2	38	256 qam	7
8	194750000	2.9	38	256 qam	8
9	202750000	2.9	38	256 qam	9
10	210750000	2.7	38	256 qam	10
11	218750000	2.5	36	256 qam	11
12	226750000	2.7	37	256 qam	12
13	234750000	2.5	38	256 qam	13
14	242750000	2.2	38	256 qam	14
15	250750000	2.5	38	256 qam	15
16	258750000	1.9	38	256 qam	16
17	266750000	1.7	38	256 qam	17
18	274750000	1.9	38	256 qam	18
19	282750000	1.7	38	256 qam	19
20	290750000	1.5	38	256 qam	20
21	298750000	2.4	38	256 qam	21
22	306750000	2	38	256 qam	22
23	314750000	2	38	256 qam	23
24	322750000	2.5	38	256 qam	24

Downstream bonded channels

Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors

1	Locked	36.6	42868425	22302
2	Locked	36.6	41735741	16440
3	Locked	37.6	2364165	9039
4	Locked	38.9	1747267	8802
5	Locked	38.6	16936	7110
6	Locked	38.6	209012	7046
7	Locked	38.6	120136	7367
8	Locked	38.9	11986	7603
9	Locked	38.9	8416	6535
10	Locked	38.9	2125622	6373
11	Locked	36.6	2159217	14578
12	Locked	37.6	15506	6957
13	Locked	38.6	55613	4727
14	Locked	38.9	3464	6375
15	Locked	38.9	9430	5443
16	Locked	38.6	4535	4490
17	Locked	38.6	6800	6579
18	Locked	38.9	2542	4670
19	Locked	38.6	2246	3471
20	Locked	38.9	2016	5091
21	Locked	38.9	1769	3692
22	Locked	38.9	2199	2771
23	Locked	38.9	2006	4084
24	Locked	38.6	1636	3260

[carlosp_uk]

Upstream bonded channels

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID

1	39400000	37	5120	64 qam	4
2	46200000	37.5	5120	64 qam	3
3	60300000	37.5	5120	64 qam	1
4	23600000	36.8	5120	64 qam	10

Upstream bonded channels

Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts

1	ATDMA	0	0	0	0
2	ATDMA	0	0	0	0
3	ATDMA	0	0	0	0
4	ATDMA	0	0	0	0

[carlosp_uk]

Network Log

Time Priority Description

05/03/2024 13:14:50	notice	LAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:40:56	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:26:11	notice	LAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:25:34	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:25:25	Warning!	LAN login FAILED : Incorrect Username / Password / ConnectionType;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:16:17	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:16:16	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 11:51:20	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 11:13:50	notice	LAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 11:13:47	Warning!	LAN login FAILED : Incorrect Username / Password / ConnectionType;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:56:32	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:56:25	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:55:48	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:55:17	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:54:42	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:54:41	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 08:33:37	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 08:33:36	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 07:44:56	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 07:44:55	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;

[Adduxi]

Unfortunately VM will insist on the Hub being in Router mode for their troubleshooting.  You will need to do a 60 second pinhole reset and then check the logs and PostRS errors.  Ideally they should remain at zero.  Rising PostRS errors usually are a noise ingress problem.  SYNC errors relate to mostly Upstream problems but you don’t seem to have any T3 errors.

[carlosp_uk]

---

@Adduxi wrote:

You will need to do a 60 second pinhole reset and then check the logs and PostRS errors.

---

They only had me do a 15 second reset, which kicked the hub out of Modem Mode and seems to have reset the firmware.  Logs have survived though.

Have I missed out on some additional benefit of the longer reset?

[Client62]

The 60 second RESET is required to trigger a complete return to the shipping condition, 
if the old logs are still present that full reset did not happen.

VM may not care how you switch to Router mode ( by reset or by the menu ).
In Modem mode VM can not remote access the state of the Hub.

[carlosp_uk]

Thanks all.

Today’s update: 

I’ve been running the hub in Router Mode as requested for 24 hours. One more day to go before a follow up with support. 

As predicted, it has made no difference, we are still getting WAN disconnection and the same SYNC errors are still accumulating in the hub’s log. Each loss of Internet connectivity coincides directly with the log messages. 

I can only hope this is enough to persuade the phone support team tomorrow to send out an engineer. This is a miserable experience - I wish they had just believed me in the first place. 

[Adduxi]

In the meantime setup a BQM ( if you haven't already?) and this will monitor your circuit.   www.thinkbroadband.com/ping

Post a link to the live shared graph for comments.  It's also evidence for any discussions with VM btw.  

[carlosp_uk]

Good suggestion - I already set up my own external monitoring script. I might do this one too.