With 3 kingside pawns still on the 2nd or 7th rank and the king behind them on the back rank, it is very easy to be mated. This is a 400 ELO error.

In Example 1, Black's rook threatens Rd1#. Moving the white rook Re1 only stalls the inevitable. Kf1 or h3 would have avoided the checkmate.

In Example 2, Qg5 is a blunder. Qd1, Kf1 or h6 would have seen off the attempted checkmate.