No Ranging Response Received T3 Time-Outs with Motorola MT7711

Afternoon folks:

  I added 200 Mbs Comcast Internet a few months ago using a Motorola MT7711 modem/router. We've had problems with Internet dropouts. Sometimes only momentary. Sometimes lasting a few hours (fairly rare). We probably get one or two per day on average. Per the modem/router's Event Log, it looks like the problem is T3 time-outs. Sometimes the MT7711 recovers from these almost instantly, sometimes it requires a power-cycle, and sometimes (more rare) we can't get Internet connectivity back for a few hours no matter what we do. When the issue lasts more than a few minutes, I've found that a nearby residential xfinity hotspot also has Internet connectivity issues. In other words, at least sometimes, other residences are being affected. Comcast keeps telling me that their diagnostic says everything is fine. However, it also appears that Comcast's diagnostics can't even tell that my modem doesn't have an IP address (when the T3 time-outs are occurring back-to-back). Yes, my modem/router might be "connected", but it is repeatedly getting T3 time-outs and doesn't even have an IP address (DHCP can't do its thing). In as much, I can't get on the Internet in those situations.

  They layout of my system is such that I have  a splitter (provided by a Comcast Tech) where Comcast's coax comes into the house. On branch goes to the Cable TV Box and the other heads about 50 feet to the other end of the house where all my network stuff is. That is where the modem/router is. The coax is quality Quad Shield Southwire (swept to 3 GHz) with quality connectors.

  Based on Internet research, it looks like the power level of the Upstream Bonded Channels is borderline. My understanding is that values near 50 dBmV indicate problems upstream of my modem/router.

  I temporarily removed the splitter to see how much the upstream power numbers changes. As expected, they got about 3 dB lower. This is what one would normally expect from a splitter. So, I don't see any problems with the splitter. I should note that the T3 time-outs still occurred with the splitter bypassed.

  I then moved the modem/router to the basement and fed it directly from Comcast's coax. The upstream power numbers got about 1 dB lower than with the splitter bypassed. This seems about right for a 50 foot run of high-quality coax. In as much, I'm not seeing any indications that there are problems inside my house. Rather, I suspect problems in Comcast's system upstream of my house (in their "plant").

  Given all of the above. Do you agree that Comcast has a problem in my area that needs to be addressed? If so, who do I speak with and what do I say? This situation is always a bit touchy when you decide to use your own modem/router. However, from what I understand,  the MT7711 is a fairly reliable modem/router. Regardless, I want to avoid being charged for a Comcast Tech to come out here when I'm fairly confident the dropouts (T3 time-outs) are not theh result of anything in my residence.

  I should note that these problems don't seem to occur regularly. Rather, they seem to come and go. For instance, I cleared the modem/router's Event Log 4 hours ago and it is still empty. However, there are other times when the T3 time-outs seem to ovvut back-to-back.

  I'd appreciate any guidance you can provide!

  Thanks, Michael