Weird result when Underscore.js, remove duplicates in array of objects based on key value

i have some weird result when i try to remove duplicates from an array of objects, let me explain this is my array is returned by a service:

var mens =[{
    "text":"Ahoy",
    "from":"9728467",
    "to":"9732825",
    "date":"2017-05-19 18:37:14",
    "idProyecto":"1",
    "foto":null,
    "fotolocal":null,
    "tipo":1,
    "sync":1,
    "privado":1,
    "descargado":0,
    "miembros":null,
    "idSyncLocal":"97284672017519183714",
    "$$hashKey":"object:96"
},
{
    "text":"Salut",
    "from":"9728467",
    "to":"9732825",
    "date":"2017-05-19 18:37:26",
    "idProyecto":"1",
    "foto":null,
    "fotolocal":null,
    "tipo":1,
    "sync":1,
    "privado":1,
    "descargado":0,
    "miembros":null,
    "idSyncLocal":"97284672017519183726",
    "$$hashKey":"object:108"
},
{
    "text":"1",
    "from":"9728467",
    "to":"9732825",
    "date":"2017-05-19 18:37:39 ",
    "idProyecto":1,
    "foto":null,
    "fotolocal":null,
    "tipo":1,
    "sync":1,
    "privado":1,
    "descargado":1,
    "miembros":null,
    "IdSyncLocal":"97284672017519183739"
},
{
    "text":"2",
    "from":"9728467",
    "to":"9732825",
    "date":"2017-05-19 18:37:44 ",
    "idProyecto":1,
    "foto":null,
    "fotolocal":null,
    "tipo":1,
    "sync":1,
    "privado":1,
    "descargado":1,
    "miembros":null,
    "IdSyncLocal":"97284672017519183744"
},
{
    "text":"3",
    "from":"9728467",
    "to":"9732825",
    "date":"2017-05-19 18:37:51 ",
    "idProyecto":1,
    "foto":null,
    "fotolocal":null,
    "tipo":1,
    "sync":1,
    "privado":1,
    "descargado":1,
    "miembros":null,
    "IdSyncLocal":"97284672017519183751"
}]

and i have this code:

var mySubArray = _.uniq(mens, 'IdSyncLocal');
document.getElementById('content').innerHTML += '<br>Some new content!' +        JSON.stringify(mySubArray);

The thing is it should return the not repeated items filtered by IdSyncLocal, but it always removes the second item, in this example all the items are different, so i dont know why is returning bad, please if someone could help me with finding some answer, i will be very thankful.