Capturing a mousemove event while mousedown over a target

I'm having some trouble with how jQuery emits it's event objects.

I'm trying to build a functionality where the user clicks a target and drags the mouse to a direction.

I then calculate the rotation to perform on an SVG element.

The problem is that when I click on that element and drag, the event object(which I naively assumed would come from the mousemove) seems to change and it comes from the mousedown of that element being pressed.

If I leave the mousemove event just how it is, without any mousedown's it seems to work just fine.

This is the code I use(mousedown's on the actual element are declared somewhere else):

$(document.body).on('mousemove', '#svgroot' ,function(event){ 
    var selected = svgCanvas.getSelectedElems(),
    root_sctm = $('#svgcontent g')[0].getScreenCTM().inverse(),
    pt = transformPoint( event.pageX, event.pageY, root_sctm ), //this is where the event object seems to change when 'pressing and holding' over this element

    mouse_x = pt.x * current_zoom,
    mouse_y = pt.y * current_zoom,

    shape = svgCanvas.getElem(svgCanvas.getId());

    var real_x = x = mouse_x / current_zoom;
    var real_y = y = mouse_y / current_zoom;

    var box = svgedit.utilities.getBBox(shape);
    console.log(selected)
    console.log(box)
    var cx = box.x + box.width/2;
    var cy = box.y + box.height/2;
    var m = getMatrix(shape);
    var center = transformPoint(cx,cy,m);
    cx = center.x;
    cy = center.y;
    var ccx = box.x // ne
    var ccy = box.y // ne

    var grip = event.target;
    var griptype = elData(grip, "type");
    var current_rotate_mode = elData(grip, "dir");


    if (current_rotate_mode == "nw")  ccx = box.x + box.width;
    if (current_rotate_mode == "se")  ccy = box.y + box.height;
    if (current_rotate_mode == "sw"){ ccx = box.x + box.width; ccy = box.y + box.height;  }
    var compensation_angle = ((Math.atan2(cy-ccy,cx-ccx)  * (180/Math.PI))-90) % 360;
    var angle = ((Math.atan2(cy-y,cx-x)  * (180/Math.PI))-90) % 360;
    angle += compensation_angle;

    svgCanvas.setRotationAngle(angle<-180?(360+angle):angle, true);
    console.log(angle);

});