Gigabit plan, blue bonded light keeps turning green, caps at 90mbps

[Pnw12]

I'm currently provisioned for gigabit, and used to regularly see 400-600mbps in actual throughput. I have no cable splitters in the house, the incoming line goes straight to the modem. 

For the past week or so, the blue bonded downlink light will turn to green within a few hours of a reboot. My download speeds have degraded to around 90mbps. Upload speeds have been fine at around 30-40mbps.

Resetting the modem will always bring back the blue bonded light, but restoring normal speeds of 400-600mbps speeds is hit or miss, and always degrades back to 90mbps after a few hours.

Does this look like an Xfinity issue? Or should I try purchasing a new modem. I currently have an Arris SB8200 that's around a year old. 

Modem Information:

Standard Specification Compliant	Docsis 3.1
Hardware Version	6
Software Version	AB01.02.053.01_112320_193.0A.NSH

Here is modem signal data:

Startup Procedure

Procedure	Status	Comment
Acquire Downstream Channel	651000000 Hz	Locked
Connectivity State	OK	Operational
Boot State	OK	Operational
Configuration File	OK
Security	Enabled	BPI+
DOCSIS Network Access Enabled	Allowed

Downstream Bonded Channels

Channel ID	Lock Status	Modulation	Frequency	Power	SNR/MER	Corrected	Uncorrectables
37	Locked	QAM256	651000000 Hz	5.2 dBmV	39.4 dB	0	0
13	Locked	QAM256	495000000 Hz	5.9 dBmV	40.3 dB	0	0
14	Locked	QAM256	507000000 Hz	5.9 dBmV	40.2 dB	0	0
15	Locked	QAM256	513000000 Hz	5.1 dBmV	40.1 dB	0	0
16	Locked	QAM256	519000000 Hz	5.0 dBmV	40.0 dB	0	0
17	Locked	QAM256	525000000 Hz	5.2 dBmV	39.7 dB	0	0
18	Locked	QAM256	531000000 Hz	4.9 dBmV	39.7 dB	0	0
19	Locked	QAM256	543000000 Hz	4.8 dBmV	39.8 dB	0	0
20	Locked	QAM256	549000000 Hz	4.9 dBmV	39.9 dB	0	0
21	Locked	QAM256	555000000 Hz	4.3 dBmV	39.6 dB	0	0
22	Locked	QAM256	561000000 Hz	4.5 dBmV	39.7 dB	0	0
23	Locked	QAM256	567000000 Hz	4.2 dBmV	38.5 dB	0	0
24	Locked	QAM256	573000000 Hz	3.3 dBmV	38.9 dB	0	0
25	Locked	QAM256	579000000 Hz	3.8 dBmV	39.6 dB	0	0
26	Locked	QAM256	585000000 Hz	3.1 dBmV	39.4 dB	0	0
27	Locked	QAM256	591000000 Hz	2.9 dBmV	39.2 dB	0	0
28	Locked	QAM256	597000000 Hz	4.0 dBmV	39.4 dB	0	0
29	Locked	QAM256	603000000 Hz	6.2 dBmV	39.7 dB	0	0
30	Locked	QAM256	609000000 Hz	6.1 dBmV	39.8 dB	0	0
31	Locked	QAM256	615000000 Hz	3.6 dBmV	39.3 dB	0	0
32	Locked	QAM256	621000000 Hz	3.1 dBmV	39.1 dB	0	0
33	Locked	QAM256	627000000 Hz	3.6 dBmV	39.2 dB	0	0
34	Locked	QAM256	633000000 Hz	4.0 dBmV	39.3 dB	0	0
35	Locked	QAM256	639000000 Hz	4.6 dBmV	39.5 dB	0	0
36	Locked	QAM256	645000000 Hz	4.9 dBmV	39.4 dB	0	0
38	Locked	QAM256	657000000 Hz	5.1 dBmV	39.3 dB	0	0
39	Locked	QAM256	663000000 Hz	5.3 dBmV	39.3 dB	0	0
40	Locked	QAM256	669000000 Hz	5.7 dBmV	39.5 dB	0	0
41	Locked	QAM256	675000000 Hz	5.4 dBmV	38.9 dB	0	0
42	Locked	QAM256	681000000 Hz	5.9 dBmV	39.5 dB	0	0
43	Locked	QAM256	687000000 Hz	5.9 dBmV	39.4 dB	0	0
44	Locked	QAM256	693000000 Hz	5.2 dBmV	39.2 dB	0	0
159	Locked	Other	722000000 Hz	7.1 dBmV	38.5 dB	103160959	0

Upstream Bonded Channels

Channel	Channel ID	Lock Status	US Channel Type	Frequency	Width	Power
1	1	Locked	SC-QAM Upstream	16400000 Hz	6400000 Hz	40.0 dBmV
2	2	Locked	SC-QAM Upstream	22800000 Hz	6400000 Hz	40.0 dBmV
3	3	Locked	SC-QAM Upstream	29200000 Hz	6400000 Hz	40.0 dBmV
4	4	Locked	SC-QAM Upstream	35600000 Hz	6400000 Hz	39.0 dBmV
5	5	Locked	SC-QAM Upstream	40400000 Hz	3200000 Hz	37.0 dBmV

Here is modem log data:

02/12/2021 05:22	2436694061	5	"Dynamic Range Window violation"
02/12/2021 05:22	82001100	5	"RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=<redacted>;CMTS-MAC=<redacted>;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:22	73050400	5	"REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=<redacted>;CMTS-MAC=<redacted>;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:22	68001102	3	"Config File Rejected due to Invalid or Unexpected TLV 11 encoding;CM-MAC=<redacted>;CMTS-MAC=<redacted>;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:22	73040200	3	"TLV-11 - Illegal Set operation failed;CM-MAC=<redacted>;CMTS-MAC=<redacted>CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:00	2436694066	6	"Honoring MDD; IP provisioning mode = IPv6"
01/01/1970 00:00	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=<redacted>;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:21	2436694044	3	"Resetting the cable modem due to docsDevResetNow"

[EG]

The signal stats are o/k but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) somewhere.

There are other signal stat figures that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They will be able to poll the CMTS to see whether or not everything is in the green zone, see your node / cable plant and modem health, and also see a history plot for the modem. You should get a reply here in your topic. Good luck !

[ComcastBillie]

Hello! I'm truly sorry to hear you've been experiencing service issues with your speeds and I would love to look into this for you further! In order to better assist you please click on my handle "ComcastBillie" and send us a private message with your full name and address.

[Pnw12]

Just an update on this thread as it's been a few days. I am really sad, and more or less ready to be resigned to this fate. Has anyone found luck with any sort of escalation process?

A quick update on status:

- So my Arris SB8200 still has the same problem - I lose the bonded light in a few hours, and speed plummets to 90mbps.

- I bought a new modem. A Motorola MB8611. It handles the situation a bit better. After a few hours, the blue solid bonded light starts blinking into a blue negotiating light, but the speed drop isn't as punishing. It looks like the Motorola modem is handling the degradation and noise better.

However, I am truly struggling with the Comcast support agents. Every few hours, I get a single reply with a single question, and the ticket gets kicked down the line to someone else. Sometimes I get the same question, sometimes I get new questions. Sometimes the question is entirely irrelevant. Maybe it's not the representative's intention, but the net feeling that results, is I feel like I'm a hot potato.

Questions' I've gotten that seem relevant and helpful:

- Can you ensure fittings are snug but not too tight? (Got it. You're worried about a COAX loose connection. That's a reasonable troubleshooting ask.)

- Is the modem plugged into wall or surge strip? (Oohh, AC interference. Didn't think of that. Let me try wall and battery (flat and sine wave UPS)

Questions I've gotten that are already answered, or irrelevant, but all delay things by hours:

- Can you reboot the modem? (Yeah, many times)

- Can we reboot the modem? (Go for it. I totally get you need to check it off the list)

- Can we reboot the modem? (Yeah... as many times as you need)

- Can you change ethernet cables? (Can't see how that affects bonding, but, sure)

- Can you check for splitters? (That was in my post, but sure, I'll check again. Nope, no splitters)

- Can you make sure your machine meets specs? (Which machine? It's all downstream of modem. But, sure)

- Can you check to make sure you're not on a VPN? (Wut? Sure, fine.)

- Is your modem and gateway integrated? (Nope.)

For those who've successfully gotten a technician, how do you do it? Is there a list of all of the questions agents ask so I can fill them in advance instead of slowly work through it over the next month?