When I got the first of my 3 "Mossad" 9mm Tanfoglio CZ clones, it had nasty recoil, way more than any CZ clone I had before did. I could also feel the slide release getting banged on pretty hard. I ordered a new recoil spring, and all was well. The one in it was pretty weak. When the others came, I ordered new springs before I shot any of them, and I would have to say they all needed them.
My guess would have been the PX4 as I was very surprised at how soft a shooter it was.