Form panel scrollbar jumps while change in fieldset in EXtjs

Question

I have a form panel created in EXtjs 4.1 in which there are 7 fieldsets. Default fieldset type is text field. Some of them are search box text fields. Form Panel has height specified. So if I scroll down to bottom of form panel and make change in fieldset (like searching for word and selecting one of the options form results), Scrollbar jumps a bit to top. This happens in update layout, Is there any way to prevent this?

My form panel code is as below.

Ext.define('MyApp.view.Form', {  
          extend: 'Ext.form.FormPanel',  
    overflowY: 'auto',  
    defaults: {  
        anchor: '98%',  
        msgTarget: 'side',  
        disabledCls: ''  
    },  
    disabledCls: '',    
    bodyBorder: false,  
    bodyPadding: '0 8 10 8',  
    border: '0',  
    waitMsgTarget: true,    
    frame: false,  
    fieldDefaults: {  
        labelAlign: 'top',  
        bodyPadding: 0,  
        labelSeparator: '',  
        msgTarget: 'side',  
        disabledCls: ''  
    },  
    defaultType: 'textfield',  
    items:[  
        { xtype: 'item 1' },          
                     {  
            xtype: 'item2'  
         },  
         { xtype: 'item3'},  
         { xtype: 'item4' },  
         {  
            xtype: 'item5'  
         },  
         { xtype: 'item6' },  
         { xtype: 'item7' }  


    ]  
});  

This is happening for all fieldset changes.