For the longest time I’d get random signal dropouts every few hours. Observing the GBS-C’s output VGA line revealed horizontal sync frequency excursions, and observing the input luma+SoG line revealed high-amplitude noise bursts at 8 MHz or so. After months of debugging and ordering a multi-hundred-dollar oscilloscope, I discovered a malfunctioning light dimmer switch in my wall was likely generating RF interference, causing my Wii to output a garbled video signal to whatever load was present (eg. GBS-C or a 75 ohm RCA terminator). My debugging log is at https://github.com/ramapcsx2/gbs-control/issues/461.