SYNC Timing Synchronization failure

Question

Hello,I seem to be suffering with occasional network disconnects from the WAN.&nbsp; I'm running in modem mode with a unifi dream machine - which notifies me every time the internet connection drops.&nbsp; Support want me to change the hub back to router mode which seems pointless.&nbsp;&nbsp;The coax cable connection looks to be tightly secured.Any help greatly appreciated.I've logged into the Virgin Media Hub 3 and see the following:01/01/2026 12:23:33noticeLAN login Success;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;01/01/2026 10:37:13criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;01/01/2026 07:58:25criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;31/12/2025 23:36:56criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;31/12/2025 23:20:10criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;31/12/2025 20:09:26criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;31/12/2025 19:36:54criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;31/12/2025 18:02:28criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;30/12/2025 03:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;27/12/2025 04:29:44criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;26/12/2025 18:30:48criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;26/12/2025 15:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;26/12/2025 02:00:20criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;26/12/2025 01:59:25criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;25/12/2025 23:55:29criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;23/12/2025 09:08:10criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;23/12/2025 03:19:38ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;22/12/2025 08:10:16criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;22/12/2025 08:07:55criticalNo Ranging Response received - T3 time-out;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;22/12/2025 05:34:23criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=&lt;&lt;REDACTED&gt;&gt;;CMTS-MAC=&lt;&lt;REDACTED&gt;&gt;;CM-QOS=1.1;CM-VER=3.0;

jpeg1 · Answer

That's not enough on its own. To monitor dropouts you need to set up a BQMhttps://www.thinkbroadband.com/broadband/monitoring/quality&nbsp; and post a live link here.The hub stats would also be useful

Roger_Gooner · Answer

It's not pointless as VM can't use TR-069 for hub management when you've got the hub acting as a dumb modem.

Adduxi · Answer

VM will always request the Hub to be set back to Router mode for diagnostics. &nbsp;

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SYNC Timing Synchronization failure

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01/01/2026 12:23:33	notice	LAN login Success;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
01/01/2026 10:37:13	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
01/01/2026 07:58:25	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 23:36:56	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 23:20:10	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 20:09:26	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 19:36:54	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 18:02:28	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
30/12/2025 03:19:39	Error	DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
27/12/2025 04:29:44	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 18:30:48	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 15:19:39	Error	DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 02:00:20	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 01:59:25	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
25/12/2025 23:55:29	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
23/12/2025 09:08:10	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
23/12/2025 03:19:38	Error	DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
22/12/2025 08:10:16	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
22/12/2025 08:07:55	critical	No Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
22/12/2025 05:34:23	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;