Light primer strikes definitely have nothing to do with bullet weight as @halfmoonclip said. There is either a problem with how far back the sear is being released in DA, or there is an issue with your firing pin/spring.Walther has the pistol and advises 5--7 business days to examine/repair, as needed.
As stated, ejection and feeding were 100% when the rounds discharged. Some required four, or five DA or SA strikes to detonate. Primers examined on unfired rounds had very tiny pin impressions. This was consistent through two boxes of factory ammo. Unacceptable.
I understand that the PPK/S is an older design. So is the 1911 and Single Action Army. All proven and reliable.
I'll bet Walther fixes mine. I'll advise.
Our Ft. Smith PPK/S loves hot defensive rounds and functions best with them. They were actually the first things we ran through it when it was new, and it ran without fault. Only weak hardball ammo exhibited any cycling issues, which seemed to have had to do with the cycling being less than completely vigorous.