[old_tv_nut]

Hum in the sync separator should make the whole picture move, but what you are seeing is the sweeps changing in amplitude. For example, the vertical has a squeezed area and a stretched area that drift upward, and the horizontal moves much more on the right than the left, which means the width is changing.
So, I am at a loss as to why this isn't reduced by filtering the supply voltages. Something is not adding up for me.