Add additional checks for en-passant possiblity when fixing the erroneus ep flag from a fen.

src/extra/nnue_data_binpack_format.h

@@ -6115,6 +6115,26 @@ namespace chess
             return false;
         }
 
+        if (pieceAt(epSquare) != Piece::none())
+        {
+            return false;
+        }
+
+        const auto forward =
+            sideToMove == chess::Color::White
+            ? FlatSquareOffset(0, 1)
+            : FlatSquareOffset(0, -1);
+
+        if (pieceAt(epSquare + forward) != Piece::none())
+        {
+            return false;
+        }
+
+        if (pieceAt(epSquare + -forward) != Piece(PieceType::Pawn, !sideToMove))
+        {
+            return false;
+        }
+
         return isEpPossibleColdPath(epSquare, pawnsAttackingEpSquare, sideToMove);
     }