jQuery Grid Plugin - jqGrid

Using new cellEdit on jqGrid. Works fine when I change a field and hit enter. However, I also have formedit enabled to perform the saving of my data via modal dialog's ajax request (mention it as I am not sure if it has an impact on the issue). The fields I edit have "editable:true" set. Look at the colModel below. On some fields when I tab from them, even though I have not changed anything it will perform an ajax call to the server. On fields where I do make a change and tab from when to the next field, it also performs an ajax call to the server and the DB get updated. But on some fields (like Street Address 2, City and Zip, no ajax call occurs when I tab from them after having made no change to their content. if I do change their value and tab they do call the ajax routine.

So couple of questions:

1. is it supposed to perform an ajax call on tabbing from the field?

2. should it perform an ajax call when tabbing from the field, even though no change was made?

3. Why does tabbing on some fields cause an ajax call and others (that are also editable) not?

                {name:'Id',             index:'Id',             width: 20,  sortable:true,  align:"center", editable:false, editoptions:{readonly:true,size:0}, search:true},
                {name:'TypeOfAddress',  index:'TypeOfAddress',  width:60,   sortable:false, align:"center", editable:true, edittype:"select", editrules:{edithidden:true,required:true}, hidden:true, resizable: false},
                {name:'StreetAddress1', index:'StreetAddress1', width:120,  sortable:true,  align:"left", editable:true, editoptions:{size:10}, editrules:{required:true}},
                {name:'StreetAddress2', index:'StreetAddress2', width:120,  sortable:false, align:"left", editable:true, editoptions:{size:25}},
                {name:'StreetAddress3', index:'StreetAddress3', width:120,  sortable:false, align:"left", editable:true, editoptions:{size:10}},
                {name:'City',           index:'City',           width:80,   sortable:true,  align:"left",editable:true, editoptions:{size:10}, editrules:{required:true}},
                {name:'State',          index:'State',          width:80,   sortable:true,  align:"left", editable:true, edittype:"select"},
                {name:'PostalCode',     index:'PostalCode',     width:40,   sortable:false, align:'center',editable:true, editoptions:{size:10}},
                {name:'Region',         index:'Region',         width:80,   sortable:true,  editable: true},
                {name:'Country',        index:'Country',        width:80,   sortable:true,  editable: true, edittype:"select", editoptions:{required:true}}