Wow, that sucks man. And I really feel for you: spending good money on a gun, especially a rare one in CA and getting these problems.
I got my G17Gen4 when they first came out, and I did have spent brass eject to my face but after 200+ rounds it just stopped. After that no problems; it functions as well as my other Gen3 Glocks. It has all the original parts in it (but I did have the two other replaced recoil spring and new ejector):
I still use the original recoil spring assembly.
In my opinion, we focus more on the problems than on the solutions. That's why we get more posts on Gen4 brass to the face, than boring reliable Glocks. They maybe isolated incidents, because maybe I'm that 1%. But I hope things work out for you.
If you want, we can compare our Glocks at the range to see if that helps.