Do I need to degauss it to have it face south?
Well, you should degauss it when you see these kinds of problems in general...
Yes, the Sanyo has a degauss circuit. All color monitors do. Whether it's working correctly is up for debate, but I'm willing to bet that it does. Did you turn it on from cold while it was facing south? If, for instance, you had it working in one orientation with good colors, shut it off, wheeled it so it faced south, then turned it back on five minutes later, the built in degauss circuit would not have fired at all. Similarly, if you turned it that way while it was on, you'd get the same effect.
If you HAVE tried a couple of cold power cycles with the game facing south, then you should manually degauss it with a handheld coil. It's also possible for the metal frame around the monitor to be slightly magnetized, so you might want to try to get that a bit too.
Surely you have a degaussing coil at this point, right Tighe? If not, I'll show you how to make one.
-Ian