Edit 2: Anyone reading this if you too have issues with the snes losing sync on the latest firmware just change the TX mode to DVI. You’ll have to use a scart audio breakout adapter of some kind to get sound but its working fine for me. Assuming your tv works with the snes.
Edit: Firmware 0.77 is the last firmware where snes works fine. My TV is a Vizio D40u-D1. Just to repeat on firmwares 0.77 and lower super nintendo runs flawlessly with no sync loss but updating to anything higher the snes will constantly lose sync. I have no idea why.
So I’ve been troubleshooting this issue on my sd2snes. On a lower firmware 0.76 for example snes works fine with no sync drops. If I run the latest firmware it loses sync every 5 seconds and the audio is choppy as hell. All the settings are default nothing changed. It’s very weird.