My set up involved the Wii looking at a monitor to use the pen and monitor as a form of graphics tablet. My initial testing was done on a very bright day and I had similar problems. I discovered that sunlight reflections coming through a window from behind my monitor was the problem - totally confusing the Wii’s infrared camera. Draping a curtain across the window solved the problem. Look for anything that might be reflecting unwanted light back into the Wii.