Slow speeds after upgrading plan and modem to MB8611

I need a real solution, not generic troubleshooting steps.

I recently upgraded from a 300 Mbps plan to an 800 Mbps plan. During checkout, Xfinity required me to upgrade my modem, so I purchased and activated a Motorola MB8611, which was one of the modems listed as officially supported.

Since activation, I am not getting anywhere near 800 Mbps. At best, I see 340 Mbps, but most of the time, it’s between 70-200 Mbps—slower than before the upgrade.

What I Have Already Tried (do not suggest these again please):

• Directly connected PC to modem (No router involved)
• Reseated and replaced coax cable
• Restarted & factory reset modem multiple times
• Confirmed firmware is up-to-date
• Tested at different times of the day

What This Tells Me

• This is NOT a local network issue (tested directly with modem).
• This is NOT a modem hardware issue (Xfinity-approved).
• This is likely an Xfinity provisioning issue, signal issue, or firmware issue.

The modem logs show massive amounts of corrected/uncorrected errors and repeating error messages every ~10 seconds.
I have seen many reports of this exact problem with the MB8611 on Xfinity, but no clear resolution.

What I Need from Xfinity Support (No Copy-Paste Responses)

• Verify my modem is correctly provisioned for the 800 Mbps plan.
• Check my signal levels and identify if there is noise or an upstream issue.
• Confirm whether Xfinity’s firmware for this modem is causing the issue.
• Schedule a technician visit if this is a physical line issue.

I do not need generic troubleshooting steps or “turn it off and on again.” I need a competent response from someone who can actually fix the problem. Please escalate this if necessary.

Attached below: Modem logs and connection status showing the errors.