Scour the void not that random
So scour the void says to get 4 random cards from your opponents graveyard, however if you use more than one scour the void, the cards you get in the second or potentially third use will be exactly the same as the first one. See screenshot. I used 2 Scour the void, got exactly the same cards in each use. Should not happen when my opponent has 21 cards in the graveyard on the second spell.
I've also noticed that if the opponent has a mana coupon in the graveyard, scour the void will always give you one.
Should add, the last four cards are what I got in my second cast, and as you can see I already had those four cards : 2 on the field, 2 in the hand.