In the diagram below, Black makes the move denoted as “Ne7” which moves the black knight on g8 move to e7.
[FEN "r1bqkbnr/pp3ppp/2n1p3/1BPpP3/8/4B3/PPP2PPP/RN1QK1NR b KQkq - 0 1"] 1... Ne7
The problem is, based on my limited knowledge about chess, “Ne7” should be ambiguous in this case since also the black knight on c6 can also move to e7.
How come we need only to write this move as “Ne7”? Is it simply a wrongfully written move?
I found this PGN online, so I have not written/played them myself. I would rather not go in and correct the moves myself, and I would rather find a way to disambiguate them correctly.
The c6 knight is pinned by the bishop on b5. Note that if the c6 knight were to move it would leave Black’s king in check, which renders any such move illegal.
Therefore it is ok in this case to write “Ne7” instead of “Nge7”, since the pin means that there is no ambiguity as to which knight moves.
This is an error.
When two pieces of the same type can move to the target square, you must specify enough information to make the move unambiguous.
The person / computer notating this should have switched to algebraic notation (g8e7) or specified Nge7.
If a human entered this, then it was human error, plus a system that doesn’t check for such errors.
If a computer entered this, it’s a bug.