There's this 64 piece chess puzzle I played through in a game against myself (using the custom FEN position feature), and it seems like there's a bug when replaying the game: http://nb.lichess.org/3Q2hLR0t
Here's the ending position: http://nb.lichess.org/3Q2hLR0tS48q
Here's the ending position: http://nb.lichess.org/3Q2hLR0tS48q