Connectivity problems in Fort Point area of Boston

We are on day 3 of a very serious network issue. Our office is located on Summer Street in Boston and we have Comcast business service (120/20). At the start of this week, Comcast upgraded our bandwidth and put a new router in place. Immediately afterward we had substantial network issues that resulted in regular outages troughout the day. During the outages we see high packet loss that appears to occur as more users come on our internal network. The outages last for sometimes 10-20 minutes, and other times up to an hour. The connectivity improves as we ramp down users (because our staff is starting to work from home due to the lack of reliability of the network).

We have had a Comcast tech come twice to our office. In both cases he confirmed there is not issue from the coax cable in our router to their termination point down the street. In the second case he replaced our Comcast router.

During the outages, we can connect direct into the local network on the router (10.1.10.x), and we also see high packet loss communicating to the router (e.g. ping 10.1.10.1 from device direct connected to router).

This issue is seriously impacting our business. I've been reading about this renewed focus from Comcast on improving their service. Is there someone who can help us here?

Dave