Intermittent Downlink connection loss, No Internet access afterwards, even when connection reestablished.

Xfinity began maintenance upgrades in the area about a month ago in the area. Lost internet connectivity. Did my standard due diligence for the home network. Swapped router for a known good one from a different network. Checked cabling and connections. Debugged with tier 1 via chat, modem appears to be connected properly. Noted the downlink connection is lost periodically. Replaced router again, with a new one. Replaced modem with a new one. Tech on site removed some splitters that are no longer needed. Service held for about a week. Downlink channel lost again. Will sometimes recover the downlink channel lock with a reboot but no internet access. Round two with tier 1, no problem detected, etc etc. Tried direct connect with a laptop to modem. For those keeping count, three routers, two modems, no luck. Another tier 1 tech came out today, pointed finger at router. Showed him no connection even with direct connect with laptop. Pointed finger at modem. Tried an xfinity modem, declared all was well, except modem wasn't provisioned and and no connection to the internet. In other words, no different than the two other modems tried to date. After they exceeded my patience, had them leave. (I'm sure its noted somewhere, I was less than pleased at his ability. I had to point out among other things multiple times that the port connection to the router matters, can't just plug the cat5 cable into any port..., that the downlink signal needs to be locked for the router to be able to get an IP address, etc... sigh).  So, long story short, I either need a tier 2 / someone with more backend experience that can dig a bit deeper or I need to start shopping the service. Would hate to have to make a change after 20+ years.

(In fairness, the first tech did seem more equipped to assist, and he rightly noted that the updates to the surrounding infrastructure may be making the signal more susceptible to noise than prior to the maintenance update.)