[4.1.0] - Random two click needed to select an option on a combo

Code:

var paisStore = Ext.create('Ext.data.Store', {
    fields: ['iIdPais', 'vcNombrePais'],
    proxy: {
        type: 'ajax',
        url: '/TEST/Generales/GetCountries'
    },
    autoLoad: true, //When the double click is randomly required, none of the following listeners gets fired 
    listeners: {
        load: function(store) {
            if (store.data.items.length == 1) {
                cboPais.select(store.data.items[0]);
            }
            cboPais.unmask();
        }
    }
}); //Sometimes I need to click twice on an option of this combo to select an option
var cboPais = new Ext.form.ComboBox({
    id: 'cboPais',
    name: 'cboPais',
    displayField: 'vcNombrePais',
    valueField: 'iIdPais',
    queryMode: 'local',
    emptyText: cboRepEstadisticoPais_Empty,
    fieldLabel: cboRepEstadisticoPais_Text,
    labelWidth: 50,
    width: 300,
    margin: '5 5 5 5',
    store: paisStore,
    lastQuery: '',
    allowBlank: false,
    editable: false,
    typeAhead: false,
    forceSelection: true,
    listeners: {
        select: function(combo, records, eOpts) {
            regionStore.load();
            cboRegion.mask();
        },
        render: function() {
            cboPais.mask();
        }
    }
}); //So this store doesn't get loaded when that happens
var regionStore = Ext.create('Ext.data.Store', {
    fields: ['iIdRegion', 'vcNombreRegion'],
    proxy: {
        type: 'ajax',
        url: '/TEST/Generales/getRegions'
    },
    listeners: {
        load: function(store, records) {
            store.insert(0, [{
                'iIdRegion': 0,
                'vcNombreRegion': txtTodos
            }]);
            cboRegion.select(0);
            cboRegion.unmask();
        },
        beforeload: function(store, operation, eOpts) {
            operation.params = {
                iIdPais: cboPais.getValue()
            };
        }
    }
}); //No options are added to this combo's list
var cboRegion = new Ext.form.ComboBox({
    id: 'cboRegion',
    name: 'cboRegion',
    displayField: 'vcNombreRegion',
    valueField: 'iIdRegion',
    queryMode: 'local',
    emptyText: cboRepEstadisticoRegion_Empty,
    fieldLabel: cboRepEstadisticoRegion_Text,
    labelWidth: 50,
    width: 300,
    margin: '5 5 5 5',
    store: this.regionStore,
    lastQuery: '',
    allowBlank: false,
    editable: false,
    typeAhead: false,
    forceSelection: true,
    value: 1,
    listeners: {
        render: function() {
            cboRegion.mask();
        }
    }
});

[4.1.0] - Random two click needed to select an option on a combo