Billabs Tri-Sync BL19C90T -- Wavy Display Problem

[Faxanadu]

I recently purchased this Billabs Tri-Sync BL19C90T from www.arcadeshop.com. I'm using it for a Ms. Pac-man reproduction using advancemame etc....When playing Ms Pac-man there is a slight "wobble" or "wiggle" to the screen. My wife first noticed it and described it as, "The screen is breathing." This is actually what it looks like. I noticed that on other games, such as Galaga, this problem is absent. I'm concluding from this that it has something to do with particular resolutions the screen is displaying. Any suggestions? The screen also seems to have a degauss issue at the upper right of the screen. Anything red in color ends up looking more yellowish. The built in screen degauss doesn't seem to be able to resolve this so I'm guessing I will have to purchase a degaussing coil. Anyway, the screen is in a horizontal position in a cocktail cabinet. When I swing the cabinet top perpendicular to the floor the "breathing" seems to go away and so does the red/yellow issue in the corner of the screen. I can understand reorienting the screen could affect the guns and hence the color, but why this "breathing" issue? Is there any monitor wizardry I'm missing?

[qrz]

interacting electromagnetic fields when in the closed position.
check positioning of cables   i.e lead dress, etc.



opening the cabinet removes the monitor from this field .

an external degaussing  certainly wouldn't hurt

[Ummon]

interacting electromagnetic fields when in the closed position.
check positioning of cables   i.e lead dress, etc.



opening the cabinet removes the monitor from this field .

an external degaussing  certainly wouldn't hurt

I had perhaps the same kind of wiggle in my candy, CGA monitor, with a computer running mame. No problems initially - then it appeared intermittently. Then it started happening all the time in certain modes, finally happening in all CGA modes I tried.  Using a different video card fixed this. ?