Either way, arcane/water slimes are where the content ends right now
Ok, I agree that you should look into it not unlocking as I've gone through this twice, the second time after your first reply. I've gotten both farms to be self sufficient, requiring all cores to have been processed, and it didn't unlock.
Of note, somehow I got a second "Process water slime core" during that run.
also saving doesn't seem to work most of the time.