I'm using a line chart and i'm allowing the user to add/remove the markers shown in the chart.
The markers that i'm showing are custom shapes, type image. For each marker I have a custom tooltip, so when you mouse over the image you'll see some information

If the chart is blank and a marker (image) is added works fine. If the marker is removed the image is still being shown, however the marker is not there... There's no tooltip poping up when mousing over the image. If I add another marker, the image from the first marker is moved to the new marker position.

If there are 2 markers with the same image and I remove one of the markers, the image is removed too and the only image that remains is the one for the only marker in the chart.

Below there's some of the code i'm using

Code:
//For adding a custom shape (the marker image)
Ext.apply(Ext.chart.Shape, {
CustomShape1: function (surface, opts) {        
        return surface.add(Ext.apply({
            type: "image",
            width:32,
            height:32,
            src: "images/customshape1.png"
        }, opts));
    }
});
Code:
//Series chart configuration
              .........
              series: [{
                    type: 'line',
                    highlight: true,
                    selectionTolerance: 32,
                    axis: ['left', 'bottom'],
                    xField: 'xField',
                    yField: 'CustomShape1',
                    markerConfig: {
                        type: 'CustomShape1',
                        size: 32
                    },
                    listeners: {
                        scope: me,
                        itemmousedown: me.onItemClick
                    }
                }],
             ........
The markers are added/removed by changing the data on the store of the chart.
Thank you in advance for your help