My Web Site Cannot be Reliably Accessed by Comcast Users

Our company web site: https://www.fastenersuperstore.com has experienced multiple outages exclusively with users trying to connect via Comcast, most recently today 10/19/2020 from 11am - 3pm CT.  This was also the case for several hours on Friday 10/16.  The previous episode to that was a month or two ago.  During these periods, Comcast users (including 90% of our employees) get a timeout message approximately 25% of the time they are attempting to access.  Our web site seems to be the only one we cannot access during these periods, the rest of the Internet functions as normal.  Users (including 10% of our employees) who have other ISPs do not have any trouble using our site during these same time periods.  Internally, we have tried changing our DNS to google, but this has not solved the problem, and we cannot expect our customers to do this even if it does. This is a very confusing and frustrating issue.  Any help at all would be greatly appreciated.