Downstream channels 33 and 37 at 7% and 22% uncorrectable codewords, all 27 others at zero

I need a technician dispatched. This is a signal problem, not a configuration problem, and I have the data.

Gateway is an XB7, Technicolor CGM4331COM. Downstream receive power is -15.1 to -16.2 dBmV across every bonded channel. DOCSIS spec floor is -15. Downstream SNR is 34 to 36 dB. Upstream transmit is 50, 50, 54, and 56 dBmV on channels 17 through 20. The nominal per-channel ceiling with four bonded channels is 51.

On top of that I have frequency-selective damage. Downstream channel 37 is running 22.4% uncorrectable codewords and 29.1% correctable. Channel 33 is at 7.3% uncorrectable and 11.3% correctable, and channel 33 is incrementing right now, in real time, while we're talking. All 27 other bonded downstream channels are at 0.000%.

I've isolated it. I'm seeing 3.3% sustained packet loss to 8.8.8.8 across 491 packets, against 0% loss over 287 packets to my own router. The loss is entirely upstream of my equipment.

I need a maintenance tech with a sweep meter to check the drop, the ground block, and the splitters, and to look for micro-reflections at the channel 33 and 37 frequencies. Two nulled channels with everything else clean points at an impedance mismatch.