I don't know the answer but I'm going to take a stab at it anyway. I reckon that after the game you are hitting the "Request a Rematch" button to generate the next game. If this is indeed the case, I suggest that you make a fresh challenge each time.
Chess960 seemingly not random.
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I've played 5 chess960 games with a friend, and I'm playing a sixth now; but the setup we've got has always been the same. Maybe it's been mirrored left to right, but the setup is always bishop, queen, knight, rook, king, rook, knight, bishop. Is there anything we need to do to get a different setup?