Motorola TS-9B Horizontal Issue

[StellarTV]

I'm hoping to get some input on a horizontal issue I'm having on a Motorola TV with the TS-9B chassis; not sure of the model as the back cover is missing.

When it's cold, it is fine. After 5 minutes, ringing bars creep in from the right side and stop at the middle, accompanied by a decrease in width. Is this going to be a defect in the damper side or the horizontal output side? I'm leaning toward bad mica. All electrolytics and tubulars are new.