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alexje
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Friday, March 13th, 2026 12:50 AM

New Modem | Internet dropping, high latency, upload speed abysmal; unusable

I recently replaced my old modem with a Nighthawk CAX80. I've gone through the XFinity app and activated it (did this yesterday). Attempted use the XFinity assistant for troubleshooting and am still having issues.

I see some errors in the event log in the modem, copied below. I've tried restarting the modem multiple times, pulled power for roughly 10 minutes to see if it could force a refresh. The old modem didn't support docsys 3.1, new one does.

Event Log
 
Time Priority Description
Thu Mar 12 19:30:47 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 12 19:30:46 2026 Notice (6) DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 12 19:30:45 2026 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 12 19:30:44 2026 Notice (6) TLV-11 - unrecognized OID;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:38 1970 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Thu Jan 1 00:00:32 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:30 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Thu Mar 12 18:46:01 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 12 18:46:01 2026 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:24 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:22 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Thu Mar 12 18:44:10 2026 Critical (3) Resetting the cable modem due to docsDevResetNow
Thu Mar 12 16:44:30 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:01:17 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:01:13 1970 Critical (3) DHCP failed - DHCP Solicit sent, No DHCP Advertise received;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:31 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:30 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Mar 11 19:55:41 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:01:35 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:01:33 1970 Critical (3) DHCP failed - DHCP Solicit sent, No DHCP Advertise received;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:35 1970 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:31 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:29 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Mar 11 19:50:56 2026 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Tue Mar 10 16:39:19 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:32 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:30 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Tue Mar 10 15:35:20 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:32 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:29 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Tue Mar 10 15:29:15 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:32 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:29 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Tue Mar 10 15:27:16 2026 Critical (3) Resetting the cable modem due to docsDevResetNow
Tue Mar 10 15:13:55 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:27 1970 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:25 1970 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Tue Mar 10 15:12:00 2026 Critical (3) Resetting the cable modem due to docsDevResetNow
Tue Mar 10 15:08:31 2026 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked 256 QAM 4 393000000 Hz 2.8 dBmV 44.6 dB 0 0
2 Locked 256 QAM 1 375000000 Hz 3.1 dBmV 44.9 dB 0 0
3 Locked 256 QAM 2 381000000 Hz 3.1 dBmV 44.9 dB 0 0
4 Locked 256 QAM 3 387000000 Hz 3.1 dBmV 44.9 dB 0 0
5 Locked 256 QAM 5 399000000 Hz 2.9 dBmV 44.8 dB 0 0
6 Locked 256 QAM 6 405000000 Hz 2.9 dBmV 44.7 dB 0 0
7 Locked 256 QAM 7 411000000 Hz 3.1 dBmV 44.9 dB 0 0
8 Locked 256 QAM 8 417000000 Hz 3.1 dBmV 44.8 dB 0 0
9 Locked 256 QAM 9 423000000 Hz 3.0 dBmV 44.8 dB 0 0
10 Locked 256 QAM 10 429000000 Hz 3.1 dBmV 44.8 dB 0 0
11 Locked 256 QAM 11 435000000 Hz 3.0 dBmV 44.7 dB 0 0
12 Locked 256 QAM 12 441000000 Hz 3.1 dBmV 44.9 dB 0 0
13 Locked 256 QAM 13 447000000 Hz 3.3 dBmV 45.0 dB 0 0
14 Locked 256 QAM 14 453000000 Hz 3.4 dBmV 45.0 dB 0 0
15 Locked 256 QAM 15 459000000 Hz 3.4 dBmV 45.0 dB 0 0
16 Locked 256 QAM 16 465000000 Hz 3.4 dBmV 45.0 dB 0 0
17 Locked 256 QAM 17 471000000 Hz 3.4 dBmV 44.9 dB 0 0
18 Locked 256 QAM 18 477000000 Hz 3.4 dBmV 44.9 dB 0 0
19 Locked 256 QAM 19 483000000 Hz 3.7 dBmV 45.1 dB 0 0
20 Locked 256 QAM 20 489000000 Hz 3.6 dBmV 44.9 dB 0 0
21 Locked 256 QAM 21 495000000 Hz 3.5 dBmV 44.9 dB 0 0
22 Locked 256 QAM 22 501000000 Hz 3.5 dBmV 44.9 dB 0 0
23 Locked 256 QAM 23 507000000 Hz 3.6 dBmV 44.9 dB 0 0
24 Locked 256 QAM 24 513000000 Hz 3.7 dBmV 44.9 dB 0 0
25 Locked 256 QAM 25 519000000 Hz 3.6 dBmV 44.9 dB 0 0
26 Locked 256 QAM 26 525000000 Hz 3.7 dBmV 44.9 dB 0 0
27 Locked 256 QAM 27 531000000 Hz 3.6 dBmV 44.8 dB 0 0
28 Locked 256 QAM 28 537000000 Hz 3.4 dBmV 44.6 dB 0 0
29 Locked 256 QAM 29 543000000 Hz 3.7 dBmV 44.9 dB 0 0
30 Locked 256 QAM 30 549000000 Hz 3.7 dBmV 44.8 dB 0 0
31 Locked 256 QAM 31 555000000 Hz 3.9 dBmV 44.9 dB 0 0
32 Locked 256 QAM 32 561000000 Hz 3.9 dBmV 44.8 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 20 5120 Ksym/sec 35600000 Hz 41.8 dBmV
2 Locked ATDMA 18 5120 Ksym/sec 22800000 Hz 41.3 dBmV
3 Locked ATDMA 19 5120 Ksym/sec 29200000 Hz 41.3 dBmV
4 Locked ATDMA 17 5120 Ksym/sec 16400000 Hz 41.0 dBmV
5 Not Locked Unknown 0 0 0 0.0 dBmV
6 Not Locked Unknown 0 0 0 0.0 dBmV
7 Not Locked Unknown 0 0 0 0.0 dBmV
8 Not Locked Unknown 0 0 0 0.0 dBmV
 
Downstream OFDM Channels
Channel Lock
Status		 Modulation /
Profile ID		 Channel
ID		 Frequency Power SNR /
MER		 Active Subcarrier
Number Range		 Unerrored
Codewords		 Correctable
Codewords		 Uncorrectable
Codewords
1 Locked 0 ,1 ,2 ,3 193 690000000 Hz 5.38 dBmV 44.9 dB 328 ~ 3767 12500341 3332771 354
2 Locked 0 ,1 ,2 ,3 194 957000000 Hz 7.98 dBmV 45.0 dB 148 ~ 3947 12745831 197780 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV

Question

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6 hours ago

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XfinityChelseaB

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2.2K Messages

22 hours ago

Hello @alexje, Thanks so much for taking a moment out of your day to leave a post on our community forum and we would be happy to help. If you could send our team a direct message with your full name, the name listed on the account (if different), and the service address associated with your account, I'd be more than happy to look into this for you. To send a Direct Message, please click on the chat icon in the top-right corner of the screen, next to the bell icon, and then type or select "Xfinity Support" to initiate a direct message.

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EG

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116.7K Messages

6 hours ago

@alexje @XfinityChelseaB 

Please circle back here and post any possible solutions for the issue here in these open public forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.

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