Most monitors will have a brief auto-degaussing on power up. Some will take a bunch of power cycles before they will correctly degauss. Normally over the course of daily use, they will correct themselves (minor gauss issues only). That's where the wand or coil comes into play. It's a much faster route and will work on more severe cases.
You could also try changing the orientation of the game (think north, south, east, west)... Rotate the cabinet or change its position within the room and see of anything changes. Many times games will interfere with other games (or appliances) in the vicinity.