Stockfish moved its king without castling early in game 51. Leela was a pawn down but had an eval advantage, the black king side rook was trapped in the corner. The engines exchanged minor pieces and Leela regained the pawn. Stockfish released its trapped rook, the game reached a QRB vs QRB position on move 30, Leela had a queen side passer. After exchanging queens Stockfish used its pieces to prevent the passer from advancing After some shuffling the engines exchanged rooks and reached an opposite color bishop ending. Leela was two pawns up but it was still a draw, the game was adjudicated on move 107.
Leela did not castle its king in game 52, the black pieces were mostly on the back rank and the engines played on the queen side. The b file was half open and Stockfish placed a rook there, its eval started to increase when it added a second rook and threatened the black b6 pawn. Leela couldn't defend the pawn, its eval was still relatively low.
After Stockfish captured the b6 pawn the engines exchanged most pieces. Leela soon realized it was in trouble, in a RB vs RB position its rook was still trapped on the king side. By the time the rook broke out it was still on the wrong side of the board. Stockfish gave its bishop and pushed a pawn to the 7th rank, Leela lost its rook to stop it.
The rook was much stronger in this position, Leela tried to protect its a pawn but Stockfish just traded the rook for the bishop. The white a pawn became a passer and raced forward, promoting first for the win. Stockfish wins a game pair, its lead is now +3.
Games 53-54 started with a 23-ply book, a popular line in the King's Indian, Orthodox variation. Leela pushed a pawn to a6 in game 53, Stockfish pushed pawns on the king side. The engines exchanged all bishops, then Leela's queen moved deep into black territory. Leela captured a pawn but it could not retreat. Stockfish gave a series of queen "checks", Leela's eval came down and the game was adjudicated. In game 54 the setup was similar. Stockfish's eval went over 1 for a while after it opened the queen side and went a pawn up. Leela regained the pawn, evals came down and the engines exchanged bishops and a pair of rooks. The game ended in a 3-fold repetition.
In game 55 the engines castled in opposite directions. Starting from move 10 there was a series of moves following long agreements in the engines' PVs. Most pieces were exchanged and the game reached a RB vs RB position with white a pawn up on move 22. Evals slowly increased, Stockfish moved its king to protect the queen side pawns, its pieces stayed on the king side where Leela had a pawn majority. The engines exchanged rooks, leaving a same color bishop ending. Stockfish's eval was over 4 for a few moves, Leela couldn't find the win and evals came down. The rest of the game was a long shuffle with a few pawns moves and exchanges. The game was adjudicated on move 191.
The engines castled in opposite directions again in game 56. Again there was a series of exchanges with long PV agreements. On move 22 only RRN vs RRB remained, and Stockfish went a pawn up.
Stockfish exchanged a pair of rooks and its eval jumped over 2. The engines traded pawns and Stockfish's eval continued to increase quickly, Leela's eval also started to increase. Stockfish managed to capture all the black pawns and it had two pawns left, one on each side.
The game continued for another 30 moves. Leela delayed the advancing white pawns as much as it could, Stockfish pushed one forward and then the other. Eventually Stockfish found a way to capture the bishop and the game was adjudicated. Stockfish wins the game pair and the lead increases to +4.
Stockfish castled long in game 57, Leela did not castle at all. There were no pawn exchanges after the start, Stockfish's eval came down to 0 and stayed there for the rest of the game. The engines opened a file on the king side and after some shuffling exchanged a pair of rooks. There was a long shuffle starting from move 32, with one pawn move. A few exchanges led to a QRN vs QRB position, then shuffling resumed. Leela lowered its eval for the draw rule on move 126.
The kings' setup was different in game 58, Stockfish as white castled long and Leela castled short. Leela pushed pawns on the queen side while Stockfish gave a pawn and opened a file on the king side, both evals came down. Leela started to plan how to get its king out of the exposed king side, meanwhile it moved its queen to protect a pawn and Stockfish thought that Leela chose the wrong square. It gave a second pawn and opened the center, its eval jumping to around 2.
The black king was out in the open and Stockfish chased it all the way to the b5 square. Leela predicted all these moves in advance yet its eval stayed low. Stockfish had to be careful not to get mated on the back rank, the attack ended with a series of exchanges that left a Q vs RR position.
It took Leela a while to see it was losing. Stockfish pushed the f pawn forward and captured the remaining black pawns. Leela's king was pushed back and Stockfish pushed a second pawn forward before the game was adjudicated. Stockfish wins another game pair, the lead is now +5.
In game 59 Leela appeared to sacrifice its queen for a knight almost immediately at the start. In fact this was the beginning of a combination that included taking the black queen with a pawn. On move 11 Leela was a pawn up with evals over 1.
Leela sent its king to the queen side and developed its queen side pieces. Stockfish gave a pawn to break up the white queen side pawns, its king moved to the king side where there was only one pawn left. The game reached a RRN vs RRN position, Stockfish got one pawn back while evals continued to increase. The engines traded a pair of rooks, all the black pawns were isolated and Stockfish tried to keep them alive.
The white rook moved forward and Stockfish couldn't stop it from taking the queen side pawns. Leela was 3 pawns up with connected passers and the game was adjudicated.
Game 60 started much more quietly. Leela castled its king, Stockfish decided not to since both sides were too exposed. Leela opened a file on the queen side, exchanged a pair of rooks and went a pawn up. Evals remained low, the engines traded R for BN and the black queen moved forward. On move 32 Leela moved its queen, immediately Stockfish's eval jumped to 24 (!!). Leela's eval predicted the next 7 moves correctly, but its eval remained low. Stockfish sacrificed a bishop and exposed the black king.
Stockfish presented 100% tablebase win scores, Leela remained confident it could hold despite the white queen being so close to its king. Stockfish exchanged bishops and moved the passer to e7, Leela had to block with a rook. Stockfish was careful not to allow a perpetual check threat, the knight came forward to protect the passer and threaten mate. Leela soon ran out of checks, its eval was over 2 and it again dropped, really having trouble in understanding the position.
Stockfish captured a pawn and exchanged queens, Leela tried to race to the line but Stockfish threatened mate in the corner, captured the rook and promoted first with check. There were two white wins in this opening, though Leela should have held the reverse. Stockfish's lead remains +5.