Frequent Internet Outage

I have checked my modem and router event logs and have come to the following conclusion.  I don't know how to get a hold of a human being anymore so I am posting here.  My wife works from home and is frequently dropping her internet connection during important meetings.  Xfinity sent a tech out last week who took one look at our Arris S34 modem connected to a Unifi Dream Machine router which is plugged into a Unifi USW Pro Max 16 PoE switch and  told us the problem was our equipment despite a previous customer service tech saying the signal to the house was unstable.  I have since analyzed modem and router event logs from this afternoon during an outage and reached the following conclusion:

My DOCSIS 3.1 modem is repeatedly logging SYNC Timing Synchronization failures, T3 ranging timeouts, and repeated upstream ranging/power adjustment events. My UniFi gateway simultaneously reports WAN Internet outages while the Ethernet link remains up. My downstream and upstream levels are within specification when the connection is stable. I'd like the drop, tap, upstream noise history, and CMTS logs checked for intermittent RF impairments.  

Xfinity has a tech scheduled to come out in 8 days.  I need this resolved before then before my wife's job is in jeopardy.