[Redeyes]

I ran a test of my own on a very large map just end-turning against a single ai.
Got the slave labor twice without effect on my capital's resource score. I had plenty of high resource low gold units in the queue, didn't see their production hasted when I got the event though I can't be certain about that.
I also noticed that if you get the same "a mineral mine has been found" twice in the same province, the second one has no effect.