I did a cap kit on a "speedy" MsPac which I believe to be one of the 19K49xx series models. That solved all the "poor image" issues and worked for about a month. Now, after a few minutes of the machine being on the screen "slams" to a narrow band as shown in the pictures below. Bumping on the glass and/or coin door (vibration) may or may not cause the image to revert to normal, only to "collapse into itself" again.

I'm suspecting a cold solder joint but would like your opinion on what the likely cause is or if the pictures allow a specific component to be judged as the culprit to prevent unnecessary "work" on an old chassis / machine.
Picture one is the "normal" screen. The other three are the "collapsed" pics.
Sincere thanks,
-=T=-