Not getting upload speeds I pay for.

Greetings,

I live in downtown Seattle and have been receiving emails last year about Xfinity's upgraded network and to "enjoy" the speed that I am paying for, I need to update my modem.  I used their chart of approved modems and bought the second one on the list, a Hitron CODA56 specifically because it has a 2.5Gb ethernet port as I have upgraded most of my work from home network to 2.5Gb & 10Gb ethernet.  The Xfinity document states that this modem will get up to 2.3Gbs download and up to 455Mbs upload. According to my account, I should be getting 1000Mbs down and 150Mbs up:

Downloads are great, with the 2.5Gb ethernet port on the modem, router, and most my computers, I can get closer to 1.2Gbs download.  Recently I was transferring a virtual machine image to a colleague  and it was maxing out the upload speed at about 20-22Mbs, far less than the 150Mbs that my account states I should be getting.  I have used the Xfinity Speed test countless times and it always hits that 20Mbs mark and never gets faster on the upload speeds.

I used the online chat to speak with a tech support rep and was told that they found an issue with a "bootfile" and would submit the fix to an automated system where it would be about an hour before it would be completed.

Didn't fix it.  Chatted again, and again, and talked to "Advanced" technical support twice.  They even sent out  a tech and he verified that I have prefect signal strength and it could be my network, so to disprove that, I connected my Mac Mini with a 10Gb ethernet directly to the back of my modem (connected at 2.5Gb) and same thing

 

At this point, I have "chatted" with 3 different techs, phone conversation with 2 techs, and 1 in-house visit and I am still stuck at 20Mbs and nobody seems to know what the problem is.

What can I do at this point to get this resolved?

Thanks in advance for any insight!!

Justin