Intermittent drops, repeated MDD message timeout / CM-STATUS Event Type Code 4 on DOCSIS 3.1 OFDM channel

Hi Xfinity team,

I am seeing intermittent WAN drops and repeated cable modem log warnings that appear to correlate with my router reporting WAN state changes. I would like help checking the RF plant / CMTS side for my service.

Equipment:

- Modem: Netgear Nighthawk CM2000

- Cable firmware version: V8.01.02

- Router: TP-Link Archer AX55 Pro

- Current modem time when diagnostics were captured: Thu May 28 16:24:46 2026

The modem remains operational overall:

- Acquire Downstream Channel: 417000000 Hz, Locked

- Connectivity State: OK / Operational

- Boot State: OK / Operational

- Security: Enabled, BPI+

- IP Provisioning Mode: Honor MDD, IPv6 only

The modem event log repeatedly shows warnings like:

MDD message timeout; CM-QOS=1.1; CM-VER=3.1;

These are often followed by:

CM-STATUS message sent. Event Type Code: 4; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.; CM-QOS=1.1; CM-VER=3.1;

Channel 193 appears to be my DOCSIS 3.1 downstream OFDM channel:

Downstream OFDM Channel 1

LockedStatus: Locked

ProfileID: 0, 1, 2, 3

ChannelID: 193

Frequency: 850000000 Hz

Power: -11.42 dBmV

SNR/MER: 40.3 dB

ActiveSubcarrier: 148 ~ 3947

Unerror: 100884714688

Correctable: 91535830673

Uncorrectable: 146375624

The OFDM channel is locked, but the OFDM power looks much lower than the SC-QAM downstream channels, and the corrected/uncorrected counts are very high.

My 32 SC-QAM downstream channels are locked. Power levels are generally around -2.5 to -4.3 dBmV, and SNR is around 43.4 to 45.0 dB. However, all downstream channels show non-zero uncorrectables. Examples:

417 MHz: Power -3.1 dBmV, SNR 44.6 dB, Correctables 3570, Uncorrectables 4157

399 MHz: Power -3.4 dBmV, SNR 44.2 dB, Correctables 8238, Uncorrectables 6523

465 MHz: Power -2.9 dBmV, SNR 44.7 dB, Correctables 5782, Uncorrectables 8490

597 MHz: Power -4.3 dBmV, SNR 43.4 dB, Correctables 1746, Uncorrectables 3105

Upstream bonded channels are locked and seem within a normal range:

16.4 MHz: 42.3 dBmV

22.8 MHz: 43.8 dBmV

29.2 MHz: 44.0 dBmV

35.6 MHz: 44.8 dBmV

40.4 MHz: 45.3 dBmV

10.4 MHz: 43.0 dBmV

The router log around these periods shows repeated WAN state changes such as WAN1_ON / WAN0_OFF, then WAN1_OFF / WAN0_ON, which seems consistent with the modem link briefly degrading or dropping.

Could someone please check the line / node / CMTS history for my modem and look specifically for DOCSIS 3.1 OFDM channel issues, MDD timeouts, uncorrectables, or downstream impairment around channel 193 / 850 MHz?

I can provide the modem MAC address privately if needed. I am intentionally not posting MAC addresses publicly.