I decided to fix this cheap unbranded scart switch. It has a function to share a signal from input B or C with the 1st input A which led to interference and
SCART Switch Roundup – VideoGamePerfection.com
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Scart Switches | RetroRGB
2 Way 3 WAY 5 Way SCART Splitter Box (Switched) with 0.5 Metre Cable
My Bandridge SVB7725 just landed (from another decade). Anyone else rocking a similar Scart switcher? Untested so far, but heard good things and hard to get hold of nowadays... : r/crtgaming
SCART DISTRIBUTOR 5 Lİ SİLVER BUTTON (ELEKTROMER)
RGC SCART Switch Reviewed | RetroRGB
2 Way 3 WAY 5 Way SCART Splitter Box (Switched) with 0.5 Metre Cable