Hi sravanithalapanti,
although admittedly a little bit late to the show.
For anyone who is still concerned:
The reason is that to emulate the restore behaviour maximize() is being called in the restore tool and afterwards a maximize listener handles the resize to the appropriate size.
As can be seen in the following snippet from maximize() it disables dragdd.
Code:
if (me.dd) {
me.dd.disable();
if (header) {
header.removeCls(header.indicateDragCls);
}
}
So it has to be reenabled like in the restore function of Ext.window.Window.