Thinking out loud...
I wonder if there is some faulty cable somewhere on the cable network that's connected to WKH.
Bad F connectors, rusty cable, someone running their own cable internally etc could potentially create noise on the network.
The higher QAM that FibreX uses would be more susceptible to noise. Adding the fact that the Technicolor's probably aren't the most resilient (assumption) could be compounding the issue.
Does anyone know the IP address of the Technicolor? The old Motorola (back on our old 10/2 connection) used to be 192.168.100.1