I don't think there is actually 2 seperate generations, but more like production runs. The very first batch had some issues, as noted in a couple infamous youtube videos, but the after that all the problems seemed to be ironed out.
Similar situation with lots of guns, and just a matter of getting over the initial hurdles in the production, and QC.
Rem 597 VTR - extractor issues
Sig Mosquito - cycling and feeding issues
Ruger SR9 - firing when dropped
S&W MP9 - mags dropping when fired
They eventually fix the issues, but not necessarily an official next generations.
I believe the changes were only in the bolt and the extractor if any.
I could be wrong but this is how I understand it.
As far as the guns EPPS has, since they are special made for our barrel restrictions, I can only assume they were made much further down the line than the first few batches.