One main problem was the recoil spring; early ones were coiled wire springs, the spring was round. It was also slightly truncated and people were "supposed" to put it in with the thin end pointing toward the hammer end, but many didn't.
IMHO it didn't matter anyway; in my Sig P238 I was sure to put it in right ..... but after a few boxes (forget exactly how many) of ammo I noticed that the thin end of the recoil spring had been, well, "scrunched" up. Interestingly the gun still functioned correctly but had the condition worsened I'd bet that would change.
I had heard about the new recoil spring from Sig so I bought some. These new ones are flat and they work, and, so far, I'm stil on the first one and no problems, no "scrunched" spring, it is just fine.
If you buy a 238 make sure it has this new flat wire spring!