If I believed he could do anything, I would agree ("I would let the field tech check the circuit out, cause if you blew a port out in the vrad he would have to change that anyway"). But my past experience much less than promising. The techs they send out run through a series of tests that never indicate the equipment needs replacement (unlike Comcast in Olympia, WA, where they did identify the problem on the first visit!).
I would think they could do something before I get home to check out the circuit to the CO. But maybe not, as you say, without a human being on my end....