Router periodically disconnects from Hitron E31N2V1 - Time Warner Internet

This question is about "Router periodically disconnects from Hitron E31N2V1", with Time Warner Cable internet and apps. I've been an TWC/Spectrum customer for years and - occasional hiccup aside - always had a good experience. The past month, though, has been a disaster.

My setup is very simple: I'm on the basic 200/10 plan, straight connection to the modem (no splitters nor other devices, I only have Internet with Spectrum), then to my LinkSys 1900ACS router. From there, I have 4 devices hardwired (through a separate 8-port switch) and 4-6 wireless devices.

It started wih the modem (an old Arris, similar to a TM822 but without voice) resetting itself randomly, once or twice a day. We would notice that Internet was down, and you could tell that the modem was basically rebooting. In a couple of minutes, the modem was back online and the router would reconnect.

Called Spectrum, they remotely confirmed there was a problem with the line, technician came out, said the issue was the cable from the street to the side of the house, and they replaced it. Problem re-occurred the same evening, new technician comes out, says there could be an issue with the cable from the side of the house to my distribution panel so we switch to another one (luckily my house had a secondary cable available).

He also concurrently switched me to a new Hitron E31N2V1 modem.

We still get random Internet shutdowns, but with the Hitron, it seems that the modem remains online (and Spectrum confirms they see no issue), but my router says there is no Internet. Moreover, it takes the router quite a bit of time to get a new IP (Internet light on the Linksys goes solid orange, indicating a "configuration issue" rather than a "hardware issue").

I got my old Netgear router, did a firmware upgrade followed by a factory reset, and put it into service instead of the LinkSys. Guess what? Same EXACT issue! Modem stays online (light is solid blue), but router loses Internet at random.

Anyways, I went to the Spectrum store to see if they could give me a different modem, and the guy (who wasn't exactly sympathetic...) told me they only use Hitrons now. Period.

As a last resort before switching to a new ISP I just ordered a Netgear CM600 modem on Amazon, approved by Spectrum for up to 400Mbps (and recommended by many as opposed to the Puma 6 or Puma 7 modems).

If any of the gurus that I see on this forum has an idea of what could be causing the behavior I'm seeing, I'm all ears.

Router periodically disconnects from Hitron E31N2V1?