dhtmlxgrid can't sort column when is grid.splitAt called

Hi, dhtmlxgrid can’t sort a column when the column type is set to dhxCalendar and grid.splitAt is invoked. can someone help me, thanks.
the source code bellow

<link rel="STYLESHEET" type="text/css" href="./codebase/dhtmlxgrid.css">
<link rel="stylesheet" type="text/css" href="./codebase/skins/dhtmlxgrid_dhx_skyblue.css">
<link rel="STYLESHEET" type="text/css" href="http://localhost:9080/webtest/dhtmlxGrid/dhtmlxCalendar/codebase/dhtmlxcalendar.css">
<script  src="./codebase/dhtmlxcommon.js"></script>
<script  src="./codebase/dhtmlxgrid.js"></script>
<script  src="./codebase/dhtmlxgridcell.js"></script>
<script  src="http://localhost:9080/webtest/dhtmlxGrid/dhtmlxCalendar/codebase/dhtmlxcalendar.js"></script>
<link rel="STYLESHEET" type="text/css" href="http://localhost:9080/webtest/dhtmlxGrid/dhtmlxCalendar/codebase/skins/dhtmlxcalendar_dhx_skyblue.css">
<script  src="./codebase/excells/dhtmlxgrid_excell_dhxcalendar.js"></script>
 
    
    <script src="./codebase/ext/dhtmlxgrid_drag.js"></script>
     <script src="./codebase/ext/dhtmlxgrid_mcol.js"></script>
       <script src="./codebase/ext/dhtmlxgrid_splt.js"></script>
       <script src="./codebase/ext/dhtmlxgrid_selection.js"></script>
    
<div id="gridbox" style="width:600px;height:210px;background-color:white;"></div>

<br>
 
<script>
mygrid = new dhtmlXGridObject('gridbox');
mygrid.setImagePath("../../codebase/imgs/");
mygrid.setHeader("a,b,c,d,e");
mygrid.setInitWidths("150,150,150,150,150");

mygrid.setColTypes("dhxCalendar,edn,edn,edn,edn");
mygrid.setDateFormat("%d-%m-%Y", "%d/%m/%Y");
mygrid.setColSorting("date,int,int,int,int");
mygrid.splitAt(2);
mygrid.init();
mygrid.setSkin("dhx_skyblue");
mygrid.loadXML("grid_formatting.xml");
</script>

the xml file:

<?xml version="1.0" encoding="UTF-8"?>
<rows>
 	<row id="1">
		
		<cell>05/01/1998</cell>
		<cell>-1500</cell>
		<cell>12.99</cell>
		<cell>-1500</cell>
		<cell>12.99</cell>
	</row>
	<row id="2">
			<cell>01/01/2000</cell>
	<cell>1000</cell>
		<cell>0</cell>
		<cell>1000</cell>
		<cell>0</cell>
	</row>
	<row id="3" selected="1">
		
		<cell>12/01/2001</cell>
		<cell>-200</cell>
		<cell>7.99</cell>
		<cell>-200</cell>
		<cell>7.99</cell>
	</row>
	<row id="4">
		
		<cell>01/01/1992</cell>
		<cell>350</cell>
		<cell>11.10</cell>
		<cell>350</cell>
		<cell>11.10</cell>
	</row>
	<row id="5">
		
		<cell>01/01/2003</cell>
		<cell>700</cell>
		<cell>7.70</cell>
		<cell>700</cell>
		<cell>7.70</cell>
	</row>
	<row id="6">
		
		<cell>30/10/1999</cell>
		<cell>-1200</cell>
		<cell>0</cell>
		<cell>1500</cell>
		<cell>12.99</cell>
	</row>
	<row id="7">
		
		<cell>01/01/2005</cell>
		<cell>1500</cell>
		<cell>12.99</cell>
		<cell>1500</cell>
		<cell>12.99</cell>
	</row>
	<row id="8">
		
		<cell>15/10/2001</cell>
		<cell>500</cell>
		<cell>9.70</cell>
		<cell>500</cell>
		<cell>9.70</cell>
	</row>
	<row id="9">
		
		<cell>12/01/1991</cell>
		<cell>400</cell>
		<cell>0</cell>
		<cell>400</cell>
		<cell>0</cell>
	</row>
</rows>

when mygrid.splitAt(2) is invoked, the column ‘a’ sort failed,
when don’t invoke mygrid.splitAt(2), the colum ‘a’ sort success, is it a bug?
can someone provide a solution? many thanks.
Note: the data type of column ‘a’ is date type

I debug the code
var cell = mygrid.cellByIndex(0, 0);

when grid is split,
cell.getDate() is null
cell.getValue = ‘05-01-1998’

and when is not split(grid.splitAt not invoked)
cell.getDate() is not null

why cell.getDate has different value between split status and not split status?

The issue is confirmed and fixed.
Please, open ticket at support.dhtmlx.com so we can provide you with a fixed version of dhtmlxgrid_splt.js