Motorola MB8611 modem frequently loses connection to Xfinity/reboots (yeah same here)

Feb 10 update:

After 54 hours up from Jan 31 to Feb2 the modem rebooted again. The modem was then back to software 19.2.20. In my support ticket with Motorola the tech said "The software version Comcast should push to your modem is 19.2.18. I don't really know why they changed it back to the 19.2.20 version. Please power off the modem for 30 seconds, power it on, and check if the software version is still 19.2.20 after the boot cycle has been completed. If no change you should contact Comcast and ask them to update your firmware with the 19.2.18 version."

I didn't pursue it (and left it at 19.2.20) mostly because dealing with Xfinity support is time consuming (among other things) and the number of reboots was tolerable since only two occurred during business hours. As of the reboot at 9:20 this morning, the software/firmware is back to 19.2.18. 

Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
10:47:01 Thu Feb 2 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
22:47:03 Thu Feb 2 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
19:10:20 Fri Feb 3 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
07:51:39 Sun Feb 5 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
02:48:15 Tue Feb 7 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
Time Not Established Critical (3)       Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Time Not Established Critical (3)       Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
16:10:51 Tue Feb 7 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
20:09:31 Tue Feb 7 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
Time Not Established Critical (3)       Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Time Not Established Critical (3)       Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
20:35:47 Tue Feb 7 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
12:53:03 Thu Feb 9 2023     Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
Time Not Established Critical (3)       Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Time Not Established Critical (3)       Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
06:11:57 Fri Feb 10 2023        Critical (3)        UCD invalid or channel unusable;
Time Not Established Critical (3)       SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
Time Not Established Critical (3)       Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Time Not Established Critical (3)       Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Time Not Established Notice (6)     Honoring MDD; IP provisioning mode = IPv6
09:20:21 Fri Feb 10 2023        Notice (6)      DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.; 
09:20:28 Fri Feb 10 2023        Critical (3)        UCD invalid or channel unusable;

Hello @user_sa. I am sad to hear you are having issues with the modem and services. It has been a couple of days, are you still having issues, or were you able to get this resolved? 

@XfinityAaron - The issue with network connectivity is still very prominent. I have experienced three Xfinity network outages in the last two and a half hours.

update: Now 4 times in the last five hours.

@user_sa Thank you for letting us know. Since this is a known issue, and unfortunately with 3rd party equipment our hands are tied in regard to any firmware updates I would suggest swapping out the device for the time being, and then reverting back to the device when a "fix" is rolled out. I would also be happy to discuss shipping our gateway out, and possible discount on the rental to make sure it is not a service issue, or you can shop new devices here. 

I would like to check on the interruptions you mentioned, can you send me a direct message, so I can take a look? 

To send a "Direct Message":

Click "Sign In" if necessary

• Click the "Direct Message chat" icon

• Click the "New message" (pencil and paper) icon

• Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears. The "Xfinity Support" graphic replaces the "To:" line

• Type your message in the text area near the bottom of the window

• Press Enter to send it

@sigs​ Looks like others are having luck getting the Moto 8611 back to  normal operation within the last day.

Working software & consistent up time.

Looks like Comcast & Moto have been able to resolve it.

Too bad my S33 is now past its return window.

But at least I am future proof with a working 8611 in the closet.

Glad I never returned it!

This is unbelievable! I had the S33 for about 6 months and kept having issues with it. I contacted Comcast via Twitter as that seems to be the best path to talk to someone who can do something and seems to be knowledgeable. I would schedule a tech to come out, only to get a recorded message the next day stating they found an issue and fixed it. Turns out their automated system was just resetting the modem! I wish I had known that, as the S33 was then past its return window. So, now I'm mad and I get them to send a tech out (they said they would waive charge, which they did). Tech said everything looks great! History on circuit/connection/whatever was also good. I ask him to look at Comcast forums and search for S33 and he says "Oh, I can see lots of other people are having issues" Duh! So, he calls supervisor, they talk a bit, and he has the nuts to suggest that I upgrade to Comcast Business - in my house! So, I say no thanks, and then he says to maybe try a different modem. So, I get the MB8611 - and more of the same [Edited: Language] The issue I was having with the S33 was it would work fine for a bit, then all of a sudden web pages would not load completely and I would have to refresh 2-3x to get it to come up completely. I get the MB8611 - and the same thing started to happen after about a week or so! Difference is, it went away on its own. So, I contacted Comcast on Twitter and they said that many people were having issues due to a firmware upgrade on the modem but it should be fixed, so fingers crossed! I will mention this (never had this happen before): When I had service initially installed, tech said I had a really hot signal! So, I am guessing that these modems can't deal with it and for some reason Comcast's own modems can. I did try to buy some attenuators and see if those would help, and they made it so it wouldn't work, but I found out later I was hooking them up in the wrong place/wrong direction.

It seems that if these are Comcast-approved modems, that they should take some responsibility to get them working! If they aren't going to bother, then stop allowing people to get their own equipment! Makes me want to start up my own ISP....

@GUS_GuyUsingSystem​ The issue is not resolved.  I contacted Comcast and Motorola about 10 days ago with the same issues everyone else is having with each blaming the other.  Motorola agreed to send a replacement MB8611 which arrived today and I started receiving drops within an hour or hooking it up.  For the past nine days I have been using a Netgear CM2000 which has worked perfectly.  I won't be buying any more Motorola products and I will use the two Motorola modems as bookends or door stops as that's about all they're good for.

@milchuck​   Do you have the old software or new (faulty = new)

Hi there @user_e5b5b5! Did the issue persist? 

@user_jason​ based on your initial signal stats it looks like you have some sort of line problem.  That doesn't necessarily mean it's Comcast's problem, just that something is interfering with your signal around 670-700Mhz.  Given that it was working for the three days you had the modem running with no splitters it's possible the issue is with your household wiring.  You could also have a dodgy line from Comcast that works ok with no splitters.  It would be helpful if you could check your signal stats again with the modem in that no splitter configuration that worked for 3 days.  If that ugly mess around 670-700Mhz goes away you probably have a wiring issue in your house (sorry, your problem) and if it's still there (but probably less bad) it could well be a Comcast issue.

@user_jason 

Is there a cell phone tower near to your location ? Some LTE services operate in the upper part of that spectrum 670 to 700 MHz. You may be experiencing some spurious noise ingress / interference leaking into the line(s) somewhere from it. Good luck !

(sidebar: is anyone else having trouble replying in forums? Last 5 days I haven't been able to post from my PC. I have been composing long replies on PC in OneNote and then pasting in from my phone. Unfortunately that seems to mean no well-formatted table, but I can post image of relevant channels. Anyway…)

I was coming back to give my update but now see the two above posts. Doesn't look like I'm getting notifications about activity now either.

So I captured connectivity stats regularly while I only had the cable modem as only device and no splitter - just joiner. At the after 3d 2h I had these stats shown at end of post. I think that would say Comcast issue per @zandor60657. They have been out and find no issue with their devices.
This of course those tests are done with my modem disconnected which means all other devices on my network are offline. This includes the T-mobile local cell box that is 1m from my cable modem. We don't have a strong cellular signal at our house so they gave us this box to cover the house. It does provide LTE. Perhaps @EG is onto something. I will now turn that off and see how we fare.

Well, local cell box doesn’t seem to be it. I powered it down. Modem restarted 6h 15m after. Then 7 minutes after that. And another pair of restarts 4h 15m later. Here is snippet of the connection stats 3h after latest restart:

I guess next I'll try modem right where line comes in. 

Initial results say there is no love for staying connected even if the troubles at higher frequencies are gone. Below will be some stats after 6h of connectivity right where line is in with an unpowered splitter to modem. (The two TV lines come out of the powered splitter behind the unpowered splitter.) The high freq errors appear gone or mitigated. (Assuming there is a problem in my house lines which those frequencies why don't techs see it with their scanners? Why does remote diagnostics (online chat) not see this as a problem? But also not as far as I know the source of the restarts.)

At 9h the modem restarted. I don't know how to get a lot of meaning out of the event log. Shouldn't there be an event that states why modem is restarting itself?

Maybe this restart is isolated. Will keep things as they are and see.

Snippet at 6h:

Hello @user_d5a98d Thanks for reaching out to our team for assistance with your connection concerns. Do you experience any issues with your connection if you bypass your router and just use your internet connection from your gateway? 

Does your modem come back online by itself? How long is your connection down when this happens? 

I have not bypassed the router directly, but I have been looking at the modem logs and see that the modem loses connection a few times a day. It always comes back after 2-3 minutes, but that will disconnect the VPN, drop all the calls, stop any live streaming. I have been watching the modem logs regularly to see if there are any patterns or particular time of day, but I have not seen any. Last week I had solid uptime for three whole days, but the issue returned, and is back to dropping a few times a day. 

@user_e5b5b5​ 

Yeah, you'll probably never know.  Could be a modem firmware update, could be Comcast fixed something, could be something else.  But hey, at least it's working!  

@user_e5b5b5​   What is your current Firmware version # on the Moto 8611?

I am very glad to hear your internet is stable now. If you do run into any issue with your service feel free to reach out to our team here.

@swilson317a​ Ha! Here is a quote from the NY Times! "The Motorola MB8611 is our pick if you already have gigabit or faster internet services: It's one of the least expensive DOCSIS 3.1 gigabit modems with a 2.5GbE port, it has a two-year warranty, and it's well designed." 

Thought I'd report back here. For some reason, Comcast still had my old modem listed on my account. Maybe I forgot to work with them to switch it. I worked with a support agent. Once I gave her the mac address of the old modem and the new one, she updated the modems on my account. I then rebooted again. When I re-checked the speed test (speakeasy.net, not Comcast's test, as Comcast doesn't include upload speed), I noticed my upload speed doubled. YAY! Am hoping this will address my issues with the internet dropping randomly. Good luck to those still having issues!