Modem intermittent ly losing connection and modem restarts

Hello, I have been having a problem with intermittent internet connection loss for two full days.

Across three different modems and two tech visits, the intermittent modem connection drops / modem automatic restarts persist.

My coax wall connection and coax from wall to modem are new as of December 2021.

During 7/27 afternoon and evening, I experienced several modem connection drops. I have been using a personally-owned Arris SB8200 since May 2020. It has always performed 100% well, and I appreciate the logs and four different lights on the front describing connection status. During these modem connection drops, I noticed the following light sequence (starting from normal Power = Green, Downstream = Blue, Upstream = Green, Internet = Green):

1. Downstream light turns green
2. Downstream and Upstream lights both flicker at a fast rate for several seconds
3. Downstream, Upstream, and Internet lights turn off
4. Modem seems to reboot and reconnect
5. Internet connection resumes

From Steps 1-3 was around 5-20 seconds usually, and modem reboot/reconnect took an additional minute or so after a period of 10-100 seconds.

In the later 7/27 evening, the connection became stable.

I work from home and have my work computer and home computer both connected via Ethernet to a personally-owned Unifi Dream Machine router. My SB8200 modem is in Bridge mode.

In the morning of 7/28, the connection losses happened a couple times an hour and became more frequent to the point of not being able to do an amount of work, it became around a 1:5 down vs up time.

I called Xfinity and the agent set up a tech appointment for that afternoon (7/28).

The tech came with me present, tested the connection at the wall, tested the connection at the hub outside my apartment, and reported that everything looked good. The tech reported "changing a port out to a brand new one" and advised to change to a new modem, so I picked up an XB8 from my local Xfinity location.

During the activation process for the XB8, the Xfinity app had trouble activating the new modem, so I called Xfinity, and the agent also had trouble. After 10 minutes, the modem activated. The modem connection seemed and acted stable.

Several hours later that evening, the connection losses returned with the XB8 at the same frequency as with my SB8200. I called Xfinity, and the agent and I both witnessed several disconnections/reconnections. The agent sounded like they saw something, and made a wondering comment about node switching or something, but was unable to diagnose anything else, so they set up another tech visit for 7/29 afternoon (today).

I did not attempt to work from home today, 7/29, because I could not risk more productivity loss. Wife who works from home reported that connection was near-unusable for her due to frequent modem internet connection losses.

The tech arrived with me present. They tested the signal at the wall, tested the signal at the hub outside my apartment unit, and reported that everything looked good. The tech switched my brand-new XB8 for a brand-new XB7, and advised that I use the XB7 as my router as well as modem to rule out any interactions with my personally-owned router. I agreed and have been using the XB7 as router and modem since the tech visit. My personally-owned router's power and Ethernet are all disconnected. There is no chance that it is doing anything in an unpowered and unconnected state.

The intermittent disconnections have persisted through the afternoon and evening until around a half-hour ago. The connection has been stable for around a half-hour now. I do not trust its stability.

Please help me. I don't know how to escalate to get someone to care to look if something on the street was bumped by construction or something, and I don't want to need to endure yet another tech visit where they test signals that will appear the same as they did two days ago and I'm sure even two months ago. Something happened two days ago somewhere because I have had nothing but 100% satisfaction with Xfinity internet for more than 6 years, and I cannot seem to get to someone at Xfinity that cares enough to stray from what feels like a path of insanity of doing the same thing and expecting a different result.