That flicker probably just comes from a glitch in the analog-to-digital converter on the old CRT unit. Those units still use a bunch of discrete ICs and a little bit of hand‑wound tuning that can drift if the power supply isn’t stable. A hacker could push a signal through the analog input to make the bars pop, but it’d take a decent amount of signal‑juggling to get a clean “message” out of the noise. If you really want to sniff it, grab a cheap oscilloscope, hook it up to the camera’s composite output, and see if there’s a pattern in the spike. Otherwise, just chalk it up to a tired old video chip having a bad day.