When Mickey 17 gets his daily memory transfer before he goes on his "death mission" (find a live specimen), there is a glitch or something and its clear a 100% memory transfer doesn't occur to the drive, pieces are missing. Mickey 18 is VERY different from every previous Mickey, he talks different but most importantly he doesn't blame himself for his moms death (red button in car).
Mickey 2-17 felt they deserved all the bad shit that happened to them because of guilt at their moms death. Mickey 18 says its not their fault their mom died, it was a faulty car part that led to the accident. He redirects his guilt into anger at the system/leaders.
Unfortunately that aspect which is one of the more interesting ideas in the movie, our memories make us who we are, isn't really explored at all in depth and just one of the 20 sub plots that kinda go nowhere. I was hoping for some more out of that whole idea, like Mickey 18 making dozens of clones of himself to do something unexpected.