[old_tv_nut]

I looked at the video again, and I'm struck by the way the lines flashed on briefly with a second or so between occurrences. This is almost like some sort of mechanically intermittent connection.

Just as a wild idea, I would try flexing all video cables and power cords near both ends, where fraying/breakage is most likely. I'd do this for the power cords of everything else on the same circuit too. I'd also wiggle all power plugs in the wall sockets in case there is a socket with a loose ground. Also, open the set and resolder all the connections to components where the power comes in.