XB8 on 2.5G / 250 Mbps plan stuck at 40 Mbps upload XB8 Gateway

I need help to reach/escalate to Advanced Repair / Network Provisioning, not basic Wi-Fi or device troubleshooting.

I am on a 2.5 Gbps download / 250 Mbps upload plan with an XB8 gateway. The XB8’s own speed-to-gateway test matches all device tests and is capped around 1000 Mbps down / 39–40 Mbps up. Wired and Wi-Fi 6E show the same upload cap.

Gateway diagnostics show no upstream OFDMA channel locked. There is no OFDMA upstream channel present.

Downstream is locked and error counts are clean. Upstream power is roughly 41.5–45.5 dBmV. This does not appear to be a MacBook, Wi-Fi, Ethernet, or customer-device issue.

I've spent over 16 hours on this issue between phone support, store visits, and Technicians. None of them understand that this is a comcast/xfinity issue.