I assume you are using component cables to connect your Wii to the OSSC? The Wii’s component output is notoriously inferior to the GameCube. Most wouldn’t notice unless they were displayed side by side. Then again, not all cables are built equally. Are you using the official Nintendo cables or a third party set? Some third party cables are well built, others not so much. If using component cables, I generally go for official cables whenever possible for the best results. Then again, I’ve used a Wii2HDMI for years and never had any issues with ringing artifacts.