Here is the manual. It is not a solid state TV, and it uses mostly tubes.
It does have a single transistor in the UHF tuner, and the B+ power supply and high voltage anode power supplies both use semiconductor rectifier diodes, but they are not using any voltage regulation. The boosted B+ power supply (Bb) uses the tube damper diode for rectification, and the audio amplifier uses the boosted B+ power.
The vertical height fluctuation is about half to one full scanline in height. So it is minor. Like I said, I replaced all electrolytic caps. I measured the old and new caps for capacitance, ESR, and current leakage (at circuit voltage). The old electrolytic filter cap, a multi-section cap, was out of spec. The new old stock multi section electrolytic that I replaced it with is well within spec after reforming it using a bench power supply.
The audio amplifier circuit appears to use C212, a 3uF electrolytic capacitor as a decoupling capacitor that is attached to the boosted B+ power (Bb). I replaced it with a 3.3uF polypropylene film capacitor, so I doubt it is the culprit, unless Panasonic skimped on the capacitance, and even when new this TV had a bit of raster size fluctuation with bass beats.
Maybe I just need to upgrade C212 to an even higher capacitance? I have worked on many 1990s CRT TVs as a hobby. This is my first non-solid state TV. So the boosted B+ power supply is a new concept to me. I read RCA’s Bernard Grob’s textbook “Basic Television”, which explains how boosted B+ increases the B+ voltage by using the residual current from the horizontal deflection damper diode.