Comcast C7100V hanging/crashing

Ok, as a way of closing out this thread, here's what Comcast found.

Overseas Comcast technical support reset the unit multiple times, pushed new configs multiple times, "corrected some file organization problems" (never explained), confirmed line levels reported OK, and admitted she had no idea what the problem might be, and ordered a truck roll.

Comcast lineman put a spectrum analyzer on the drop and reported "typical" levels, but as I'd reported trouble he replaced the drop wire and one piece of outdoor wiring, gaining perhaps 1.5 dB from before. Declared the drop to be textbook perfect as measured at the modem interface.  C7100V still continued to hang and recover, hang and recover.  Between failures when I could log into the web UI, I noted that both upstream and downstream channels had good power and S/N ratio, and ZERO errors of any kind.

Comcast lineman pulled out the brand-new C7100V that was hanging and re-installed the old "failing" one.  Long back-and forth with his partner at the NOC to get the telephone service up and running, but it finally came up as well.   I reconfigured the router to NOT provide a guest AP, NOT maintain logs except for security issues, and basically turn off every product feature I could.  It's kept running for 22 hours now.

I did a factory reset on the new one and will take it back to my retail store for a refund.