Vertical height changes with beat of bass tones in the audio

[LukeSimon]

I have a late 1960s Panasonic AN-72 that I replaced all electrolytic, paper, and oil capacitors in. Before replacing the caps, there was extreme distortions in the raster such as a rolling horizontal warping of the horizontal deflection with what looked like a 60hz hum bar. After replacing the caps, everything is great except for a very subtle decrease and subsequent increase in the vertical height whenever there is a bass beat like a bass drum beat. Higher pitched beats do not cause the vertical height to change.

Which parts of the circuit can cause this? Can it be in the IF stages, or is this just a decoupling capacitor and resistor in the audio section that are out of spec?