Zone 3.3 blunders

In many ways I was puzzled at what happened at the Zone 3.3 Championship. The top two seed, GM NGUYEN Ngoc Truong Son was held to early draws while Filipino GM Julio Catalino Sadorra lost two consecutive games, one of them to a sub 2000 player.

Malaysian FM Yeoh Li Tian is in the lead with 6/7 drawing two games. His success was probably due to the low number of inaccuracies in his games while many others were struck by some really bad blunders.

Look at the following diagrams.

FM Liu Xiangyi - GM Megaranto

 White is just winning after 39. b7 Rb8 40 Rc1 and 41 Rc8 is unstoppable. Instead he played 39. Be4?? Rd8+ 40 Ke2 g4, black exchanged pawns and sacrificed his knight for the white b-pawn to reach a drawn R+B vs R ending.

IM Goh Wei Ming - Novendra Priasmoro

After sacrificing an exchange, White has started mopping up black pawns. In this position, his b5 pawn is almost unstoppable. Now 40 Kh2 getting his king of the back rank and attacking the black rook is winning. However he played 40 b6?? Rxf3 41 b7 Rxd1+ 42 Kh2 Rb3 allows black to stop the pawn and eventually draw.

FM Liu XiangYi - GM Sadorra

Even the 2nd seed was not immune to blunders. In the above diagram,  white has just checked on f3. What should black play, how should he get out of check? 42....Qf7?? The worst possible move as 43 c6 and the pawn just cannot be stopped.