Here is a puzzle I got out of Sudoku, Volume 11 by Bendon. It is puzzle 143 if you have the book. The book answer has a typo in it as their final solution shows initial numbers in the wrong place.
I have checked my solution backwards and forwards and find nothing wrong. It shows that in cells A7, A9, G7 and G9 either a 5 or an 8 can work, yielding a workable solution.
Take a look and let me know what you think.