for example. one square 2 or 7 fits in the 2 empty squares and then the square above has exactly the same square position and the same 2 numbers to left use. Very easy to pick the wrong position top square 2 and 7 and bottom square is then 7 and 2, and vice versa. I'm not alone in this happening there have been examples screenshot before where this happened.I'm sorry!!!! a Sudoku with multiple solutions is INVALID!!!!
I realise there are Sudokus with NO solution and Sudokus with multiple solutions but they ARE INVALID!!!!
The only valid Sudoku has ONE solution ONLY!!!!