Jquery Ajax "The parameters dictionary contains a null entry for parameter" error

I've run into a problem with my AJAX call.

$.ajax({
  url: "/Admin/changeStudentPhoto/",
  type: "POST",
  data: {
    file: file1,
    filename: filename1,
    studentID: studentID1,
    x: x1,
    y: y1,
    w: w1,
    h: h1
  },
  success: function(data) {
    //do Stuff
  },
  error: function() {}
});

It sends the request to this controller:

public JsonResult changeStudentPhoto(string file, string filename, int studentID, double x, double y, double w, double h) { 
  // More Stuff 
}

The thing is that by applying a breakpoint on the call I can see that the parameters are properly set, I get an error 500 from the controller that includes an error:

The parameters dictionary contains a null entry for parameter 'h' of non-nullable type 'System.Double' for method

The specific parameter does not really matter, before h it was the studentID.

I usually place data directly in the URL but this time I need to also pass a base64 string so I can't place it in a URL.

Thanks in advance.

EDIT: Added pics for clarification