Frequent packet loss, disconnects with CM1200 modem and 600Mb Plan

Hello! I've been experiencing connectivity issues and packet loss with my Internet service for quite some time. The severity of the problem varies substantially from hour to hour, ranging from rock-solid through various degrees of packet loss and all the way to hour-long connection failures. Interestingly, even when packet loss is occurring, uncorrectable codewords are not reported.

I recently updated my Comcast package to a new plan with a higher speed tier (600Mb vs. 250Mb). The problem began shortly thereafter; my connection had previously been quite good.

Here is the current channel data from my modem:

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Correctables	Uncorrectables
1	Locked	QAM256	29	639000000 Hz	4.2 dBmV	39.6 dB	1	0
2	Locked	QAM256	1	459000000 Hz	4.6 dBmV	40.9 dB	0	0
3	Locked	QAM256	2	465000000 Hz	4.7 dBmV	40.8 dB	0	0
4	Locked	QAM256	3	471000000 Hz	4.8 dBmV	40.9 dB	0	0
5	Locked	QAM256	4	477000000 Hz	5 dBmV	41 dB	0	0
6	Locked	QAM256	5	483000000 Hz	5 dBmV	40.9 dB	0	0
7	Locked	QAM256	6	489000000 Hz	4.8 dBmV	40.8 dB	0	0
8	Locked	QAM256	7	495000000 Hz	4.7 dBmV	40.7 dB	0	0
9	Locked	QAM256	8	507000000 Hz	4.9 dBmV	40.7 dB	0	0
10	Locked	QAM256	9	513000000 Hz	5 dBmV	40.7 dB	0	0
11	Locked	QAM256	10	519000000 Hz	4.9 dBmV	40.7 dB	0	0
12	Locked	QAM256	11	525000000 Hz	4.7 dBmV	40.5 dB	0	0
13	Locked	QAM256	12	531000000 Hz	4.6 dBmV	40.4 dB	0	0
14	Locked	QAM256	13	543000000 Hz	4.3 dBmV	40.2 dB	0	0
15	Locked	QAM256	14	549000000 Hz	4.4 dBmV	40.3 dB	0	0
16	Locked	QAM256	15	555000000 Hz	4.4 dBmV	40.1 dB	0	0
17	Locked	QAM256	16	561000000 Hz	4.3 dBmV	40.1 dB	0	0
18	Locked	QAM256	17	567000000 Hz	4 dBmV	40 dB	0	0
19	Locked	QAM256	18	573000000 Hz	3.9 dBmV	40 dB	0	0
20	Locked	QAM256	19	579000000 Hz	3.9 dBmV	40 dB	0	0
21	Locked	QAM256	20	585000000 Hz	4.3 dBmV	40 dB	0	0
22	Locked	QAM256	21	591000000 Hz	4.3 dBmV	40 dB	0	0
23	Locked	QAM256	22	597000000 Hz	4.4 dBmV	40 dB	0	0
24	Locked	QAM256	23	603000000 Hz	4.3 dBmV	39.9 dB	1	0
25	Locked	QAM256	24	609000000 Hz	4 dBmV	39.7 dB	0	0
26	Locked	QAM256	25	615000000 Hz	4.1 dBmV	39.7 dB	1	0
27	Locked	QAM256	26	621000000 Hz	4.5 dBmV	39.7 dB	1	0
28	Locked	QAM256	27	627000000 Hz	4.6 dBmV	39.6 dB	2	0
29	Locked	QAM256	28	633000000 Hz	4.3 dBmV	39.5 dB	0	0
30	Locked	QAM256	30	645000000 Hz	4.2 dBmV	39.6 dB	1	0
31	Locked	QAM256	31	651000000 Hz	4.6 dBmV	39.8 dB	2	0
32	Locked	QAM256	32	657000000 Hz	4.6 dBmV	39.8 dB	0	0

Upstream Bonded Channels

Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	1	5120 Ksym/sec	17300000 Hz	44 dBmV
2	Locked	ATDMA	2	5120 Ksym/sec	23700000 Hz	45 dBmV
3	Locked	ATDMA	3	5120 Ksym/sec	30100000 Hz	46 dBmV
4	Locked	ATDMA	4	5120 Ksym/sec	36500000 Hz	45.5 dBmV
5	Locked	ATDMA	5	1280 Ksym/sec	41200000 Hz	48 dBmV
6	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
7	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
8	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	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	159	722000000 Hz	7.5 dBmV	40.5 dB	1126 ~ 2969	77616108	29	0
2	Not Locked	0	0	0 Hz	0 dBmV	0.0 dB	0 ~ 4095	0	0	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

Extended Upstream Transmit Power

Enable Extended Upstream Transmit Power (checked, greyed out)

Here is a sample event log from a rough patch, showing a pattern of dynamic range window violations:

Time	Priority	Description
Mon Jul 13 19:50:48 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:57:57 2020	Warning (5)	Dynamic Range Window violation
Mon Jul 13 17:57:57 2020	Warning (5)	RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:57:37 2020	Warning (5)	Dynamic Range Window violation
Mon Jul 13 17:57:37 2020	Warning (5)	RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:57:20 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:57:18 2020	Warning (5)	Dynamic Range Window violation
Mon Jul 13 17:57:17 2020	Warning (5)	RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:56:49 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:56:18 2020	Warning (5)	Dynamic Range Window violation
Mon Jul 13 17:56:18 2020	Warning (5)	RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:56:18 2020	Warning (5)	Dynamic Range Window violation
Mon Jul 13 17:56:18 2020	Warning (5)	RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
Mon Jul 13 17:56:18 2020	Warning (5)	Dynamic Range Window violation
Mon Jul 13 17:56:18 2020	Warning (5)	RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;

And here are the troubleshooting steps I've already tried:

Resetting the modem.
First and second level tech support, which included resetting and reprovisioning the modem, hooking a PC directly to the modem to bypass internal equipment, etc.
Trying a Comcast-supplied replacement modem.
Replacing the wall-to-modem coax cable with a Comcast-supplied cable. (There are no splitters on the interior side of the wallplate; I don't know the details of how this house was originally wired for cable.)
Inspecting the wallplate (including the connection on the back side). No apparent problems there.
Run Net Uptime Monitor and other connectivity checkers over several weeks to verify that the problem doesn't seem to correlate with anything I'm doing at the time (it occurs even when I'm not here, for example) and that the house wired and wireless networks are sound (I've never seen packet loss on connections among my local devices; and when the problem occurs, it affects all wired and wireless devices in the house simultaneously).

Any other things I should try short of "have Comcast roll a truck and check the exterior connection"? Thanks in advance for any advice.

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kickaha

Frequent packet loss, disconnects with CM1200 modem and 600Mb Plan

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