Internet drops every night for around 5 minutes

I've been having this issue for 6+ months where my internet drops once a day every day.  Have communicated with Xfinity tech support numerous times each time they indicate they are boosting the signal or some other buzz word and problem continues every night.   Finally got them to sent a tech, charged me $100, they could not find a problem, said all signal levels were fine but still they replaced the Xfinity modem and problem continues.   It started more than 6 months ago while using my own Motorola modem, thinking my equipment was the problem I opted to replace it with the Xfinity rented equipment and the problem continues.  I am on my 3rd Xfinity modem as they keep telling me to replace it and I do in order to keep them working on the problem yet the problem continues.   The modem actually goes offline as if I go into my Xfinity app (using cell service since my internet is down) it shows my gateway offline and it comes back up in about 5 minutes.  The current cable run to my house is only about 2 years old so it is new although I have had my Xfinity (formerly Comcast) for nearly 25 years!  When my internet is online it tests as very good, speed is running faster than what it is rated for and no issues with speed or connectivity until it drops out for 5 minutes between 7pm and 9pm. 

So again, the internet completely drops between 7pm and 9pm every night, it is very rare that it does not happen.   It occurs weather I am using anything on the internet or not, I know it happens as my google device will show on the screen no internet access when it occurs or if i am streaming something of course it stops and the xfinity app shows my modem offline.  It even occurs if I have something directly plugged into my modem (no wifi) which makes sense since the Xfinity app shows my modem offline.  As far as I know it only occurs once a day 7pm to 9pm.  

What Xfinity equipment is shared between neighborhoods in a community that can cause this sort of problem/5 minute outage and how do we get Xfinity to identify the problem and fix it? 

As I said I have contacted tech support over and over and cant seem to get a resolution.   I doubt the problem is local to me as my neighbor says it happens to them.  Additionally a local facebook page for the community that I live in,  people all over the community are reporting the exact same problem on their Xfinity going offline for about 5 minutes every single night between 7pm and 9pm.   They have also contacted tech support and had techs come out but the problem never gets resolved.  Since a large group of people are experiencing the exact same problem at the exact same times for less than 5 minutes every night it seems very likely the problem is an area issue with equipment, either something is resetting or switching or some equipment is defective causing the outage every night 7pm - 9pm.   Since the outage is less than 5 minutes no one at Xfinity claims to see any problem when they look at it which is true, by the time someone looks at the problem everything is back online.