MXQ Adv. Sudoku

Strange 2 Cell Chains RC Ripples

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In extremely difficult grids, 1 in 10 have an occurrence of an exclusive pair that allows a sub row/column eliminations. This is strange in that once the initial sub row/column eliminations are completed, it is rare to go back to that strategy after a more complex strategy has been applied. The sequence is as follows:

This particular cascade doesn't occur often but when it does, if missed, the grid is unsolvable.

Strange 2 Cell Chains