Weird encoded polyline

[frinux]

While encoding GeoJSON into encoded Polyline, I detected sometimes that the result is not what is expected.
Here is the GeoJSON:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "LineString",
        "coordinates": [
            [
                -0.55461,
                47.497491
            ],
            [
                -0.554074,
                47.497393
            ],
            [
                -0.553654,
                47.497298
            ],
            [
                -0.553135,
                47.49717
            ],
            [
                -0.552639,
                47.497018
            ],
            [
                -0.552086,
                47.4968
            ]
        ]
      },
      "properties": {}
    }
  ]
}

And the encoded polyline:

iz{`HhikBRkBPsAXeB\\cBj@mB

Here is a screenshot of both GeoJSON and polyline on a map:

It seems that a single point is wrong encoded (the fifth one) : [-0.552639,47.497018] is encoded as (47.49702,-0.55329)

Is there something wrong with the algorithm implementation?

[frinux]

My bad, the encoded polyline has been "corrupted" by my PHP framework, which escapes backslashes...
When escaping is removed, the original polyline is well formated, as expected?
Sorry for the trouble :/