A friend of mine that I used to go shooting with owned a PPK, and it was pretty picky about what ammo you put in it. I personally saw it malfunction repeatedly one time, even though he was using new namebrand factory ammo.
In the PPK's defense though, a number of handguns in that size range tend to do the same thing. Just experiment with different brands and loads, until you find the right ammo for it.
The "fit and finish" of the PPK's are excellent, but they're still somewhat overpriced.