Motorola Quasar Vertical Issue

[mcmlxv]

Just took delivery of a Motorola Quasar TS-915 with a chassis date of 11/68. The set is in excellent original condition and is operational. The set initially presented with a vertical issue: the vertical height expands to full screen then shrinks top and bottom by an inch or so. Within a few days, the set lost vertical hold, and the bottom third of the screen showed an upside down, folded image.

I replaced the video drive and vertical amp panels with NOS units, cleaned the mounting pins, and cleaned and reseated the convergence panel. The picture now fills the full screen and the vertical hold has returned. However, the picture suffers from intermittent vertical judder and the image is rolling occasionally.

Any ideas?