Found an old episode of the 1971 London Weekend TV series “Doctor At Large” on YouTube. It’s in Black & White due to the 1970/71 Colour Strike, which in and of itself is one bizarre concept, but not really relevant here. Starting around here in the episode, while the show’s characters in the forefront remain (mostly) stable and in focus, the background wavers up and down in a sea-sickness inducing pattern (the background is stable for seconds here and there, mostly when everyone is stationary).
Since I doubt LWT at this time used digital filming technology (actually the proof is that this episode is B&W and the workers simply turned off the colour tubes during the colour strike), what optical properties in the field of analog filming would have been causing this?
ETA: Not really Café Society material, as I am interested in what’s causing the effect, not the history of the series or actors.