My first Walther, a pre-64 PPK in .32 was dependable and accurate. However when the price went nuclear in '66, I let it go, and have regretted it. Since then I've owned well over 200 PPs and PPKs, PPKSs and never found one to be fully reliable even with hardball and far worse with HPs, even after throating, polishing and new springs in the magazines.
The problem with the Walther design seems to be just one thing, which was fixed in the Makarov. That is that the cartridge in the Walther is seated way to low, below the chamber, when it arrives at the top of the magazine for loading by the returning slide. Take a look at the way the Makarov has the round at the top of the magazine almost to the level of the chamber and right ready to slip in with the returning slide. The difference is huge, from a mechanical standpoint, and seems to make all the difference regarding failures to feed.
I have no idea why my first PPK functioned better. Perhaps, since I never considered it a defensive piece, I just didn't notice that it was unreliable. And, perhaps since it was my first pistol, I didn't expect it to be flawless. I don't know. It may just be a factor of selective memory which is what makes the "good old days" so good.