Currently using a Motorola MG7550 (attached screenshots are from this device).
Prior devices were a Netgear C7000 v2 and a Comcast (CISCO) DPC3941T. All had the same symptoms as current Motorola router.
I've had intermittent internet cutouts since I moved into my current home in October 2017. They were very infrequent and I chocked it up to "that's just the way it is". Since 2 weeks ago, the problem has become much more prevelent. I had been on the fence about buying my own modem/router for some time before the problem got worse so I went and did so...hoping it would fix the issue.
First modem was a Netgear c7000 v2. Activated it with Comcast and immediately started getting internet dropouts. The event log was littered with T3 timeout /range response issues. After Googling how to remedy this, I found numerous posts from people with the same issue with that particular router. After contacting Netgear support for help with the matter, I was told that "they have a firmware update available that fixes the issue but it's awaiting approval from Comcast before they can release it". I have no clue if that's true but that's what I was told. The large number of posts from other people with the same issue told me that this wasn't the product for me. So I returned it and got a Motorola MG7550. Other people had excahnged for the same unit and reported a much better experience and that it fixed their internet dropouts.
Now using the Motorola MG7550 and am still having random dropouts / T3 timeout issues.
As for troubleshooting: I have replaced the "cheap gold colored" splitter between the wall plate and cable box/modem with an Antronix 5-1000 mhz 2 way 3.5 dB. Took my coax wrench and verified that all connections were snug (but not too tight). All the cables inside the home are RG6 and have compression ends. I checked all those after reading the connection troubleshooting sticky here.
Any other suggestions before I call and schedule a tech visit?
EDIT: I've added the values from the Comcast modem in case they help.
I've asked an employee to check the CMTS for real-time and historical RF signal reports from your modem. They can also check your local node/plant for any degradation or error reports. You can expect a reply in this thread.