Here is Andrew Stuart's version. His solver will not finish a puzzle if it believes it has more than one solution:
The solver at https://www.sudoku-solutions.com/ was able to work out the answer by brute force but it didn't know how to get to it using human logic. That's perfectly reasonable. Writing a solver to use all known human solving strategies is a major undertaking:
This is what John Musgrave, a member of the Sudoku Puzzles Facebook group, had to say about this puzzle. You can see his own puzzles at http://www.manifestmaster.com
