I am not good at pure engineering theory. Just bench
theory, there are places for both.
To us a drive line was a bit of hoz fold over caused by the
H. osc or H out. Usually on the right IIRC.
You may have had a snivet, IIRC caused by oscillations in the
H out tube. Reason for multiple tubes either the tubes were
low quality or maybe something else is off a little. Look to the
screen grid decoupling cap.
Again IIRC another cure was a magnet around the H out tube.
Very common in the olden days.
73 Zeno