I just bought my OSSC and it’s been a pleasure for every other console except my snes. I’m aware of the issues this particular system has and its weird off spec refresh rate. However looking at multiple TV compatibillity lists and a video on youtube of a man using his SNES on the OSSC on the same vizio d40u-d1 his worked without issue even in line triple mode. Mine how ever shows the image and blinks black every 5 seconds or so. I tried all the different line multiplier modes to no avail. I’m just wondering why despite having a tv that’s supposed to work with the OSSC and SNES it doesn’t and if anything can be done about it. I checked my scart cable which I purchased from retrogamingcables.co.uk and it’s just fine. If anyone knows anything about this please let me know.
It’s possible something changed in the OSSC or TV firmware over time that affected compatibility.
If the video you mentioned is Bahn Yuki’s, that’s from over two years ago, and he said he was using OSSC firmware 0.72. I do recall someone else having compatibility issues with OSSC firmwares past 0.76, so you may want to try reverting to 0.76. (Remember to get the -aud version if you have a 1.6 OSSC or a 1.5 with the audio board.)
Oh my god changing it to DVI mode did the trick! I suppose the wonkey refresh rate of the SNES was making the audio cut out thus making the tv lose sync. Good thing I have a scart audio breakout adapter. I use a sound bar with my tv which features both line in 3.5mm audio optical audio bluetooth and rca input. Thanks so much Paul!