Sudden Spike in Data usage

Before anyone from Comcast replies, just know I have a $300 modem, night hawk Netgear and a $650, EERO pro6E wifi set up.  I can accurately track all my data usage per device by day and even show live data.  This has happened once before and comcast corrected it.  The last several months my data usage shown by comcast matched exactly with my EERO reports, all was good.  But starting last month, November, comcast showed 950 GB of usage and my EERO only 643 GB and I was on a camping trip for a full 8 days with 0 usage. That's almost 50% more data usage showed by Comcast.  Now, just 3 days into Dec. comcast is showing 134 GB, while Eero is only showing 64 GB and that is 100% more data usage reported by comcast.  Something is not right.  I have called and they have no answers.  They told me someone would call me back from a specific department that handles data usage and nothing.