I have turn on the options that you can not buy if its sold out. But some customers can buy it anyway. Its happens every now and then. Like with this product: https://www.veganermat.no/glutenfritt/jeezly-orginal/Its sold out/out of stock and its say so but still someone can buy it.
its very frustraiting, is it in another browser or is it a bug somewere on cscart. i cecked the mobilversion and its not there and neither in chrome and explorer