Bingo! We are actually in a power fail right now (Seattle storm) so I took the opportunity to kill everything and re-torque L1, L2 and N. I did not do the receptacle thing, as the lights oscillating happened without the TV (just happens faster with TV). So I opened these connections, re-positioned the cable and torqued the lugs to 12 NM (no documentation I could find as to the torque). It seemed that this was just a tad bigger than what they were. So far so good. We are on generator, turn the oven on, turn the TV on and I only get a small dip as the oven cycles on and off, but otherwise the voltage is stable. Will continue to monitor throughout the power outage, but so far this looks like a fix. Anyway, I am unable to create the problem.