Solving very hard puzzles sometimes has repeated numbers within a row/column or square

[sourcequench]

This one doesn't work

-2--46---
-1--8---5
-----138-
9--72-1--
8---3---2
--1-54--9
-543-----
1---6--5-
---41--3-

+-------+-------+-------+
| 3 2 8 | 5 4 6 | 7 1 1 |
| 7 1 6 | 2 8 3 | 4 9 5 |
| 4 9 9 | 5 7 1 | 3 8 6 |
+-------+-------+-------+
| 9 4 5 | 7 2 8 | 1 6 3 |
| 8 6 7 | 1 3 9 | 5 4 2 |
| 2 3 1 | 6 5 4 | 8 7 9 |
+-------+-------+-------+
| 6 5 4 | 3 9 7 | 2 2 8 |
| 1 7 3 | 8 6 2 | 9 5 4 |
| 7 8 2 | 4 1 5 | 6 3 7 |
+-------+-------+-------+