Internet Seemingly Randomly Disconnects throughout the Summer

We've been having an issue with our home internet over the past year that has completely stumped myself and 3 Comcast technicians. Over the summer, the internet seems to randomly drop throughout the day, taking around 5ish minutes or more to start working again. With everything being online these days this has become increasingly annoying and disrupting. The weird thing about this issue is it goes away over the fall, winter, and spring months only returning in the summer. As we are in CA we have brainstormed that the heat may have something to do about it. Though I cannot think of why. Below you'll find things we have tried so far to fix it.

Things we have tried:

• 3 different modems (Arris Surfboard, Netgear CM600, and the standard-issue Comcast modem) all have demonstrated the same issue.
• Replaced the entire coaxial cable run from our splitter to the modem.
• Modified and experimented with different power levels on our modem at the behest of the Comcast technicians.
• Tried 3 different routers, currently using a TP-Link Deco S4 with the default Comcast modem in bridge mode.

I am at my wit's end as Comcast support increasingly fails to address the issue doing no investigation work. All the tech does is look at the modems settings, declares everything looks solid and proceeds to tell me everything should be working fine when clearly it does not. Any knowledge and/or suggestions would be greatly appreciated.