CTX CVP-5468NI picture increased width then shrank

[luRaichu]

I've been making use of this VGA monitor with various computers since I got it in March, but its most recent application was as a monitor for my Linux box. That's when I started using the 1024x768 @ 60Hz (XGA) mode often.
Well, a few days ago I was in a white-on-black fullscreen terminal and suddenly the picture width increased drastically. I cranked up the vertical size. The horizontal geometry became distorted and the right edge was folding over. Then, I saw the picture shrink towards the center of the screen and I quickly hit the power button.
I turned the monitor back on a few hours later to be greeted with a dim, shrunken XGA image.
But, the picture is perfectly fine and bright in the 640x480 (VGA) and 800x600 (SVGA) modes.
Here are some pictures of the monitor with the back shell removed. It's fairly clean inside, no visible signs of leaking caps or other damage.









A google search with "5468NI" in quotes returns a few pages mentioning this monitor and repairs.
https://crtdatabase.com/crts/ctx/ctx-cvp-5468ni
https://asavage.dyndns.org/Monitors/monitors.html (search in page for 5468)
https://pe2bz.philpem.me.uk/Html_faqs/Monitortips.htm (search in page for 5468)
I'm inclined to think that a component in one of the horizontal circuits has failed and is bringing down HV or B+, after all XGA is the highest mode supported and therefore highest stress. I'll have to look over the example multisync SVGA monitor block diagram and see how these things really work (coming from CRT TV repair where the frequencies are fixed).
Any feedback would be appreciated. I really want XGA mode to work again on this monitor. It looked really good especially when driven by modern video cards which output very crisp VGA signals.