Why does Xfinity disable my 2.5G port on my modem?

I have a 10G ethernet network at home, 10G, 2.5G, 1G switch.  I connected my Cat6e cable to the Xfinity Modem 2.5G and it was working well for about 1 month (I was getting 1.2-1.3Gbps download).  I run logging so I know exactly what and who is going thru my xFinity Modem.  

About 30 days later I suddenly lost connectivity but ONLY on the 2.5G port (all the 3 other ports were fine).  I ran some diagnostics and all was on on the Xfinity Modem except the 2.5G port.  I logged into the Xfinity modem and all was as it should be 

Model: CGM4981COM

Hardware Revision: 2.0

LAN Ethernet Port 4 showed Connection Speed: 2500Mbps

So I went into Troubleshooting to check the logs and noticed what seems to be some sort of  Xfinity login id?? (note these logs don't provide much info, just login user and date/time) at the same time my 2.5G port stopped working.

So I ran my own diagnostic tools and it looks like "some data" was definitely sent by Xfinity.  Obviously I can't positively say Xfinity disable the 2.5G port, but the coincidence seems very fishy.

Now, I pay for the fastest possible bandwidth to my home (there is no higher tier), not cheap.  But I can no longer use the 2.5G port and I can only use the 1G port so my downloads are 700-900Mbps.

Should I take the Xfinity Modem back to an Xfinity store or is this something Xfinity have intentionally done?

[Edit: Personal information]