Nighthawk X6S Tri-Band Range Extender intermittent drops in connection with Cox broadband.

I have the latest firmware on Modem/Router/Extender (CM700, X6 R8000, X6S EX8000 Tri Band Extender) and I still have intermittent drops in connection.  I play Xbox One X and almost every evening i receive a "Lost connection to Xbox Live" message and I am unable to connect unless I reboot modem/router/extender.  I get around 300mb dl / 30mb up from Cox when everything is working fine but the drops in connection are very frustrating.  I had Cox come out last week as they were seeing some signal issues in their lines.  They replaced some connections and removed a signal reducer (sorry for the non tech term) that they believed was causing the issue.  Internet worked "OK" for a few days and it's now acting up again.  I tried to install old firmware for both my router and extender but that didn't help.  I'm not a complete idiot when it comes to computers/tech but when it comes to home networking I feel totally lost when trying to troubleshoot the issue.  Is there a simple way to determine what is causing the loss in connection?  Any apps, programs etc that I can download to monitor my connection with?  I've read about ping plotter and other programs but don't know how to use those.  Any and all help is appreciated!  Thank you!

Josh

Las Vegas