Dynamic Range Window violation

O/k even though the signal stats looked o/k at that snapshot in time, the error log entries may indicate that something is going on. Perhaps there is noise ingress into the line(s) / an upstream channel-return path impairment 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 can check the CMTS (Cable Modem Termination System) for any real time degradation and / or error reports, see your node / cable plant and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and poll for those upstream receive signal stats.

You should get a reply here in your topic. Good luck !

Thanks!

Status
The statuses listed show the connection state of the cable modem. They are used by your service provider to evaluate the operation of the cable modem.

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

Downstream Bonded Channels
Channel   Lock Status   Modulation   Channel ID    Frequency      Power        SNR    Corrected   Uncorrectables
1           Locked        QAM256         9       471000000 Hz    3.6 dBmV    35.9 dB    23261         16077
2           Locked        QAM256         1       423000000 Hz    2.9 dBmV    36.1 dB    29179         15400
3           Locked        QAM256         2       429000000 Hz    3.0 dBmV    36.1 dB    30653         15541
4           Locked        QAM256         3       435000000 Hz    3.2 dBmV    36.0 dB    28440         14842
5           Locked        QAM256         4       441000000 Hz    3.1 dBmV    36.0 dB    28830         15727
6           Locked        QAM256         5       447000000 Hz    3.4 dBmV    36.0 dB    26109         15517
7           Locked        QAM256         6       453000000 Hz    3.5 dBmV    36.0 dB    25764         15478
8           Locked        QAM256         7       459000000 Hz    3.6 dBmV    36.0 dB    25354         16573
9           Locked        QAM256         8       465000000 Hz    3.8 dBmV    36.0 dB    25291         16446
10          Locked        QAM256         10      477000000 Hz    3.8 dBmV    35.9 dB    23790         17178
11          Locked        QAM256         11      483000000 Hz    3.7 dBmV    35.8 dB    22753         17600
12          Locked        QAM256         12      489000000 Hz    3.6 dBmV    35.7 dB    22091         16692
13          Locked        QAM256         13      495000000 Hz    3.6 dBmV    35.7 dB    24008         17005
14          Locked        QAM256         14      507000000 Hz    4.3 dBmV    35.3 dB    23298         18188
15          Locked        QAM256         15      513000000 Hz    4.3 dBmV    35.6 dB    22171         18333
16          Locked        QAM256         16      519000000 Hz    4.4 dBmV    35.5 dB    24249         17659

Upstream Bonded Channels
Channel     Lock Status     US Channel Type     Channel ID     Symbol Rate     Frequency     Power
1             Locked            ATDMA               3         5120 Ksym/sec   29200000 Hz   45.5 dBmV
2             Locked            ATDMA               1         5120 Ksym/sec   16400000 Hz   47.4 dBmV
3             Locked            ATDMA               2         5120 Ksym/sec   22800000 Hz   45.7 dBmV
4             Locked            ATDMA               4         5120 Ksym/sec   35600000 Hz   44.0 dBmV


Current System Time: Tue Feb 23 10:57:55 2021

That's not what that message means. The upstream power level is fine !

Arris is wrong ! They have been passing the buck and have been conning people with that statement lately !! They are probably trying to cover up for their liabilities about the lawsuits against them because of their use of the horrible Puma 6 chipsets... Only the Comcast plant / engineering specs matter;

Specification Min Max
Downstream Power Level
Cable Modems -10dBmV +10dBmV
Gateways and EMTAs -7dBmV +7dBmV
Downstream Signal to Noise Ratio 35dB -
Upstream Power Level +35dBmV +50dBmV
Upstream Signal to Noise Ratio 31dB -
Upstream Receive Power -2dBmV
+2dBmV

Something else is going on.

Please post a screenshot or C+P all of the text of the signal status padge. Include the downstream channel stats. And post the error log entries in their entirety.

The above log are the only entries made today.  Below is a screenshot of the status around the time of the second error. (I've tried several times to upload a png to this response and all I see is a yellow triangle.  Hopefully you're able to see it. 
In case it doesn't show, here's a link to the file: https://forums.xfinity.com/t5/media/gallerypage/image-id/50788iC1FCE8A24EDE823D )

Can't see your pic. Since you are a new poster, it needs to be approved by a Forum Admin. That could take some time. In the interim, you could try hosting it at one of those free third-party pic hosting sites like Imgur or Photobucket and post the link to it here.

Or as stated, copy all of the text of the status page and paste it into the body of your next post here.

Welcome to our Xfinity forums, @ReluctantOne! Thank you so much for taking time to reach out about your internet connectivity issues. Please send me a Private Message with your name and address so I can take a closer look at the signal levels. 

To send a private message, click my name " ComcastEmilyS", then click "send a message".