See this game for reference. Here, the bot tried to play e1g1 (O-O), while the rook in question has already been captured.
10:54:29.922 [pool-2-thread-7] WARN net.marvk.chess.lichess.GameThread - Failed to play move Move{source=E1, target=G1, coloredPiece=WHITE_KING, promoteTo=null} in game o3tr315Q
See this game for reference. Here, the bot tried to play
e1g1
(O-O
), while the rook in question has already been captured.