Sudoku no 539 (Unsolvable)

I ran my puzzle creation program and it produced the one below, which has a Hodoku score of 5398. This usually equates to a score of between 600 and 800 in Andrew Stuart's grader and solver so I was surprised when it said it was unsolvable:

Play online 

Andrew Stuart's grader and solver 

www.sudoku-solutions.com 

sudoku9x9.com/smartsolver.php