Upstream OFDMA instability, T3 timeouts and packet loss

My OFDMA upstream channel (ch 43) changes profile on a fixed 10-minute timer. Every 10 minutes it moves from profile 10 to 12, then falls back to 11 and 10, usually within a few minutes. I notice an increase in packet loss and frequent T3 timeouts during these profile changes. After replacing the wiring and connectors on my side of the demarc, I believe the problem is outside my home.

Setup

• Modem: Netgear CM3000, firmware V6.01.04
• Plan: 2 Gig
• Wiring: direct run from the ground block to the modem. New quad-shield RG6, compression connectors, no splitters, no amplifier.

Troubleshooting

• Replaced all in-home coax and connectors between modem and handoff.
• Temporarily bypassed house run and ground block. The upstream problem did not change.
• Rebooted the modem. Cycle continues - it restarts on the new boot time, and it does not clear on its own.

Cycling

This repeats continuously, day and night, every 10 minutes. Example from the modem event log (6 cycles in a row):

17:53:06 to 12, 17:54:21 to 11, 17:55:51 to 10
18:03:06 to 12, 18:03:36 to 11, 18:04:21 to 10
18:13:06 to 12, 18:14:06 to 11, 18:15:21 to 10
18:23:06 to 12, 18:24:21 to 11, 18:26:06 to 10
18:33:06 to 12, 18:33:36 to 11, 18:34:21 to 10
18:43:06 to 12, 18:43:51 to 11, 18:45:21 to 10

The change to 12 comes exactly every 10 minutes, to the second. The return to 10 usually takes a few minutes, and is different each time.

Packet loss

I have continuous pings to multiple destinations directly from my router. Loss % depends on the upstream profile at that moment:

• on profile 10: about 0.1% packet loss
• on profile 11 or 12: about 0.5% packet loss, sometimes over 1%

T3 timeouts repeat throughout the day, and many happen within seconds of a profile change. Two examples:

• 06:05:05 T3 time-out, 06:05:20 to 11, 06:05:50 to 10
  06:20:35 T3 time-out, 06:20:50 to 10

For every lost ping, a packet capture on my router's WAN port shows the request leaving and no reply arriving. The loss appears to happen beyond my equipment.

Signal levels

Downstream (0 uncorrectables on all channels):

• 32 SC-QAM channels, 387 to 573 MHz: -1.2 to +1.8 dBmV, SNR 43.0 to 45.3 dB
• OFDM ch 193, 722 MHz: -3.2 dBmV, SNR/MER 41.1 dB
• OFDM ch 194, 957 MHz: -6.3 dBmV, SNR/MER 38.4 dB

Upstream power:

• 4 SC-QAM channels, 16.4 to 35.6 MHz: 47.8 to 48.0 dBmV
• OFDMA ch 43, 36.2 MHz: 41.3 dBmV, profiles 11 and 13

Full status page and event log below (MACs redacted).

Request

Can someone from Xfinity look at the upstream data for OFDMA ch 43 and check the line past my demarc? Happy to share my account details in a DM and schedule a tech visit if necessary.

Downstream Bonded Channels
Ch  Lock    Mod     ID  Freq (MHz)  Power (dBmV)  SNR/MER (dB)  Corrected  Uncorrectables
 1  Locked  QAM256  20       501.0          -0.1          44.1          0               0
 2  Locked  QAM256   1       387.0           1.7          45.3          1               0
 3  Locked  QAM256   2       393.0           1.8          45.3          0               0
 4  Locked  QAM256   3       399.0           1.6          45.2          1               0
 5  Locked  QAM256   4       405.0           1.7          45.2          1               0
 6  Locked  QAM256   5       411.0           1.4          44.7          1               0
 7  Locked  QAM256   6       417.0           1.3          45.1          1               0
 8  Locked  QAM256   7       423.0           1.1          45.0          1               0
 9  Locked  QAM256   8       429.0           1.0          45.0          1               0
10  Locked  QAM256   9       435.0           1.0          44.8          2               0
11  Locked  QAM256  10       441.0           0.8          44.8          0               0
12  Locked  QAM256  11       447.0           0.6          44.6          1               0
13  Locked  QAM256  12       453.0           0.4          44.6          0               0
14  Locked  QAM256  13       459.0           0.7          44.7          1               0
15  Locked  QAM256  14       465.0           0.6          44.5          0               0
16  Locked  QAM256  15       471.0           0.8          44.6          1               0
17  Locked  QAM256  16       477.0           0.3          44.3          0               0
18  Locked  QAM256  17       483.0           0.3          44.3          1               0
19  Locked  QAM256  18       489.0           0.1          44.2          0               0
20  Locked  QAM256  19       495.0           0.1          44.1          0               0
21  Locked  QAM256  21       507.0          -0.1          44.1          1               0
22  Locked  QAM256  22       513.0          -0.4          43.9          1               0
23  Locked  QAM256  23       519.0          -0.6          43.7          0               0
24  Locked  QAM256  24       525.0          -0.5          43.8          0               0
25  Locked  QAM256  25       531.0          -1.0          43.4          0               0
26  Locked  QAM256  26       537.0          -0.6          43.7          0               0
27  Locked  QAM256  27       543.0          -1.1          43.3          0               0
28  Locked  QAM256  28       549.0          -0.8          43.0          0               0
29  Locked  QAM256  29       555.0          -0.9          43.3          0               0
30  Locked  QAM256  30       561.0          -0.8          43.4          0               0
31  Locked  QAM256  31       567.0          -0.9          43.3          0               0
32  Locked  QAM256  32       573.0          -1.2          43.2          0               0

Upstream Bonded Channels
Ch  Lock    Type   ID  Freq (MHz)  Power (dBmV)
 1  Locked  ATDMA  18        22.8          48.0
 2  Locked  ATDMA  19        29.2          47.8
 3  Locked  ATDMA  20        35.6          47.8
 4  Locked  ATDMA  17        16.4          48.0

Downstream OFDM Channels
Ch  Lock    Profiles    ID  Freq (MHz)  Power (dBmV)  SNR/MER (dB)  Subcarriers  Uncorrectables
 1  Locked  0,1,2,3     193       722.0         -3.22          41.1   448 ~ 3647               0
 2  Locked  0,1,2,3     194       957.0         -6.32          38.4   148 ~ 3947               0

Upstream OFDMA Channels
Ch  Lock    Profiles  ID  Freq (MHz)  Power (dBmV)
 1  Locked  11,13     43        36.2          41.3

Event log (most recent)
Tue Oct 20 12:54:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:45:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:39:21 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:36:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:35:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:27:21 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:26:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:17:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:15:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:11:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:09:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 12:00:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:56:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:54:51 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:50:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:41:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:30:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:21:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:21:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:13:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 11:05:21 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:57:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:57:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:50:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:43:51 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:40:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:31:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:30:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:25:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:20:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:18:21 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:10:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:06:21 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 10 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:04:51 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:04:36 2026  Critical (3)  Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 10:00:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 09:50:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 09:45:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 11 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 09:37:06 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 12 13; New Profile: 11 13.;CM-QOS=1.1;CM-VER=3.1
Tue Oct 20 09:30:36 2026  Notice (6)  US profile assignment change. US Chan ID: 43; Previous Profile: 10 13; New Profile: 12 13.;CM-QOS=1.1;CM-VER=3.1