Zooming in on chart causes data to disappear.

Code:

Ext.define('MyApp.view.charts.line.Basic', {
    extend: 'Ext.Panel',
    xtype: 'line-chart',
    title: 'Prototype Display for Aircraft Flight Times',
    draggable: true,
    resizeable: true,
    
    tools:[{
        type:'search',
        tooltip: 'Undo Zoom',
        handler: function(event, toolEl, panelHeader) {
            var chart = Ext.getCmp('timechart'),
                interaction = chart && Ext.ComponentQuery.query('interaction', chart)[0],
                undoButton = interaction && interaction.getUndoButton(),
                handler = undoButton && undoButton.handler;
            if (handler) {
                handler();
            }
        }
    }],
    
    initComponent: function() {
        var me = this;


        this.myDataStore = Ext.create('Ext.data.JsonStore', {
            fields: [
                {name: 'ACTUAL_DATE', type: 'date', dateFormat: 'd-m-y'}, 
                {name: 'HRS', type: 'int'}
            ],
            proxy: {
                type: 'ajax',
                url : 'app/store/charts/airTime.php',
                reader: {
                    type: 'json'
                }
            },    
            autoLoad: true
        });
           
        me.items = [{            
            xtype: 'cartesian',
            id: 'timechart',
            width: '100%',
            height: 500,
            store: this.myDataStore,
            insetPadding: 40,
            interactions: {
                type: 'crosszoom',
                zoomOnPanGesture: false
            },
            axes: [{
                type: 'numeric',
                position: 'left',
                grid: true,
                fields: ['HRS'],
                renderer: function (v) { return v; },
                minimum: 480000,
                maximum: 660000
            }, {
                type: 'time',
                step: [Ext.Date.MONTH, 2],
                dateFormat: 'd-m-y',
                groupBy: 'year,month,day',
                position: 'bottom',
                grid: true,
                fields: ['ACTUAL_DATE'],
                fromDate: new Date('1/1/00'),
                toDate: new Date('7/1/13'),
                label: {
                    rotate: {
                        degrees: -90
                    }
                }
            }],
            series: [{
                type: 'line',
                axis: 'left',
                xField: 'ACTUAL_DATE',
                yField: 'HRS',
                style: {
                    lineWidth: 4
                },
                marker: {
                    radius: 2
                }
            }]
        }];


        this.callParent();
    }
});