I have a 19 inch arcade monitor that is a 60 in 1 multi with random horizontal jittering and shaking, it comes and goes, but it can last for a day or so. ive tried Googleing this but came up with nothing.
The 4600 series has two upright daughter cards. Sometimes the cards become loose, or the solder on the main board develops cracks (cold solder joint) and this can be the cause of the shaking.