The first thing I also thought of was the ripeness.
You purchased an expensive and supposedly very good product.
Don't give up on it so soon.
Play with it, put it through its paces. We have a fancy mandoline tucked away, which we rarely use and cannot even remember the brand. With the two of us it is usually just as easy to take out a knife, and we both have pretty decent knife skills for just your average Jane and Joe cooks. But the mandoline works great when we need it.
Don't know the advantages of V shape rather than straight cut, ours I believe is straight cut. But if one were significantly better than the other, everyone would buy just one.
Am sure there are folks who will be along to help more than I can. But as I say would keep trying. Sometimes it takes a while to learn how to use a specific product.
Before criticizing a person, walk a mile in his shoes - then you are a mile away and you have his shoes!