Most of the Martins I have seen came from the factory with high action. When played that way, if you clamp a capo on it, the strings get stretched just a bit, and it goes sharp.
There is nothing basically wrong with Martins, except for some made in the 70's, but they have to be "set up".
Sure, it's like buying a new Mercedes and having to get someone to tune it up before you can go anywhere in it. However, once you get it set up, it takes a damn good Taylor to keep up.