As soon as you have satisfied yourself that it is faulty.
And it goes back to the retailer you bought it from, not to Sony.
So that will depend if you bought it from a bricks and mortar shop, or online, or what.
Contact them, express your dissatisfaction, and ask for a return and a refund.
Respond however you think fit when they suggest a repair; the most powerful argument for a refund rather than a repair is to show them the same or similar showroom models displaying the same fault.
OTOH, if they don’t, and this shows your set is truly faulty, you might accept a repair or a replacement.
YouView Superuser, but not an employee of YouView, nor retained by them for this purpose. It's purely me speaking
