It’s not fit for purpose. They’ve had a chance to make it right and haven’t. It’s not reasonable to expect that from new, nor for you to buy another whilst they have another go.
I'd junk it off and get something else. I had similar issues with a Schuberth S2 a few years ago, the visor mechanism was crap so I just returned it and got a Bell instead.
My S3 has a really good mechanism, but it does fog up at low speeds unless open a little, despite the lid being quite well ventilated. A previous helmet of mine did this after I'd had the visor off. It's as if the two sides are not synced up.
