Nah, all model Saturns can output great RGB with the right cable (see http://retrorgb.com/saturn.html). I can personally recommend the cables from https://www.retrogamingcables.co.uk/ and from https://www.ebay.de/usr/thefoo.83, they both make their own cables and seem to know what they’re doing. For Saturns it’s important to note the difference between NTSC & PAL consoles. The PAL ones don’t do csync, so many ‘universal’ cables use sync-on-luma or sync-on-composite. thefoo.83 sells universal cables that output csync with a sync stripper that’s actually installed in a little box on the console side of the cable. If you only ever want to use your NTSC Saturn I’d recommend just getting an NTSC csync cable.
I can’t promise you this will fix your issue, but if nobody else has any better idea getting a quality cable from a reputable seller might be a good idea. Cheap cables frequently miss required components, are sometimes wired wrong and can cause all kinds of picture/audio problems.