Needs repair – Sudoku 16 Monster Review

Since the 6 star puzzles were added, I have had 3 puzzles which were faulty. I would not have a space where a character could be placed within a 4x4 square. I could remove a previously entered character and add the one I couldn't place instead. In other words, it was approving 2 different characters for the same space. And the removed character would not have another place where it could go.
Review by Jimbo30000 on Sudoku 16 Monster.