Daily Internet drops, not sure how to proceed with troubleshooting tips

About a month ago, an Xfinity tech came to the house on a call about very intermittent connectivity. He replaced every coax connector in the house, including a splitter, and replaced our modem with a new xFi gateway. (I have no secondary router.) I had hopes this would fix our daily drops, but it has not. I have been tracking our outages using Net Uptime Monitor, and I have included the last four days' logs below.

I have done what I can with this page:

https://forums.xfinity.com/t5/Your-Home-Network/Internet-Troubleshooting-Tips/m-p/3310447#M316652

I can rule everything out as far as the signal level section, then I get lost. The video was somewhat helpful, but not entirely. I can find these levels on my gateway page (http://10.0.0.1/ - the other IP goes nowhere on my network), but I have no idea how to interpet them. I can say that downstream channels average about -2.7 dBmV across the board, and upstream channels are about 47.0 dBmV.

Uncorrectable code words number in the tens of thousands. The event log shows little apart from messages relating to opening ports for my Plex Media Server. I'm happy to provide any of this information in more detail, I'm just not sure how to do it here at the moment.

I would be very eager to hear any advice on how I might proceed, hopefully at a technical level I can get my head around. I'm actually fairly technical (I work in IT) but this is not my area of expertise.

Net Uptime Monitor log, emphasis mine:

8/20/2020 6:22:16 AM 0:27:27 <<<<<<<<<<<<<<<
8/20/2020 1:09:38 PM 0:00:29
8/20/2020 1:40:48 PM 0:43:24 <<<<<<<<<<<<<<<
8/21/2020 4:23:44 AM 0:00:24
8/21/2020 5:44:33 AM 0:00:29
8/21/2020 12:51:44 PM 0:00:36
8/21/2020 12:58:53 PM 0:00:23
8/21/2020 1:05:06 PM 0:00:25
8/21/2020 1:12:16 PM 0:07:12 <<<<<<<<<<<<
8/21/2020 1:26:03 PM 0:03:10
8/21/2020 3:21:12 PM 0:00:44
8/21/2020 3:23:12 PM 0:00:23
8/22/2020 3:14:59 AM 0:00:24
8/22/2020 3:48:55 AM 0:00:44
8/22/2020 9:45:14 AM 0:01:38
8/22/2020 10:48:12 AM 3:29:49 <<<<<<<<<<<<<<
8/23/2020 3:34:04 AM 0:00:32
8/23/2020 4:56:07 AM 0:00:37
8/23/2020 8:23:01 AM 0:00:22
8/23/2020 1:18:42 PM 0:00:53
8/23/2020 1:29:41 PM 0:02:31
8/23/2020 1:32:26 PM 1:31:50 <<<<<<<<<<<<<<<<<