Intermittent connection issues (MB8600 "UCD invalid or channel unusable")

Starting a few months ago, my Motorola MB8600 cable modem seems to have intermittent issues with its connection to Comcast. Usually it lasts a few minutes, and might happen once every few days, but it's pretty bad today, and it's repeatedly happening today. The log lines below from the cable modem appear to correspond to time periods when we experience Internet problems.

13:23:47 Mon May 22 2023	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;
13:34:19 Mon May 22 2023	Critical (3)	UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
13:34:19 Mon May 22 2023	Critical (3)	No Ranging 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;
13:34:24 Mon May 22 2023	Critical (3)	UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
13:34:24 Mon May 22 2023	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;
13:34:25 Mon May 22 2023	Critical (3)	UCD invalid or channel unusable;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
13:46:05 Mon May 22 2023	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;

And here's the connection status information:

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	20	567.0	0.8	46.3	0	0
2	Locked	QAM256	13	525.0	-0.1	45.8	0	0
3	Locked	QAM256	14	531.0	0.7	46.4	0	0
4	Locked	QAM256	15	537.0	0.3	46.0	0	0
5	Locked	QAM256	16	543.0	-0.3	45.7	0	0
6	Locked	QAM256	17	549.0	-0.8	45.4	0	0
7	Locked	QAM256	18	555.0	-0.4	45.5	0	0
8	Locked	QAM256	19	561.0	0.7	46.1	0	0
9	Locked	QAM256	21	573.0	0.4	45.9	0	0
10	Locked	QAM256	22	579.0	-0.3	45.5	0	0
11	Locked	QAM256	23	585.0	-0.4	45.2	0	0
12	Locked	QAM256	24	591.0	0.6	45.7	0	0
13	Locked	QAM256	25	597.0	1.2	46.0	0	0
14	Locked	QAM256	26	603.0	1.2	46.1	0	0
15	Locked	QAM256	27	609.0	0.4	45.7	0	0
16	Locked	QAM256	28	615.0	0.2	45.6	0	0
17	Locked	QAM256	29	621.0	0.7	45.8	0	0
18	Locked	QAM256	30	627.0	0.9	45.9	0	0
19	Locked	QAM256	31	633.0	1.0	46.1	0	0
20	Locked	QAM256	32	639.0	1.0	46.0	0	0
21	Locked	QAM256	33	645.0	0.5	45.7	0	0
22	Locked	QAM256	34	651.0	0.3	45.6	0	0
23	Locked	QAM256	35	657.0	0.3	45.5	0	0
24	Locked	QAM256	36	663.0	0.9	46.0	0	0
25	Locked	QAM256	37	669.0	1.4	46.3	23	0
26	Locked	QAM256	38	675.0	0.9	45.4	16	0
27	Locked	QAM256	39	681.0	0.4	45.5	0	0
28	Locked	QAM256	40	687.0	0.4	45.5	0	0
29	Locked	QAM256	41	693.0	0.5	45.8	0	0
30	Locked	QAM256	42	699.0	1.1	45.9	0	0
31	Locked	QAM256	43	705.0	1.5	46.0	0	0
32	Locked	QAM256	44	711.0	1.5	45.9	0	0
33	Locked	OFDM PLC	193	957.0	1.0	45.3	1099967223	6161

Upstream Bonded Channels

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	17	5120	16.4	47.5
2	Locked	SC-QAM	19	5120	29.2	48.3
3	Locked	SC-QAM	20	5120	35.6	48.3

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Intermittent connection issues (MB8600 "UCD invalid or channel unusable")

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