AC1900 C7000 disconnects every other day with Xfinity

I recently purchased the Nighthawk AC1900 based on very high recommendation from Best Buy.  About every other day it completely disconnects and I have to set it up again as a brand new router with Xfinity.  I am ready to take this back to Best buy today and try to return it and advise them to stop recommending it to their customers.  My old router never did this.  I confrimed there is no issue with Xfinity connection.  Any suggestions? (Firmware is up to date).