Sometimes jqgrid getChangedCell not return checkbox changed - jqgrid

Question

when I insert/update table data. i use getChangedCell function for making input data before call API. like this.
let inputData = _$myTable.getChangedCells('all');
$.ajax({
type: "POST",
url: "/api/services/InsertData",
dataType: "json",
data: inputData
})
Please check sample image.
First I check checkbox. after then click save button.
At this moment, generally _$myTable.getChangedCells('all') return the correct value.
But, sometimes _$myTable.getChangedCells('all') return []
Table options are :
_$myTable.jqGrid({
mtype: "GET",
datatype: "local",
autowidth: true,
shrinkToFit: false,
cellEdit: true,
colModel: [
{
name: "id",
key: true,
hidden: true
},
...
],
onSelectRow: function (id) {
if (id && id !== optionlastsel) {
_$myTable.jqGrid('restoreRow', optionlastsel);
_$myTable.jqGrid('editRow', id, true);
optionlastsel = id;
}
},
afterEditCell: function (rowid, cellname, value, iRow, iCol) {
var checkboxNameSet = _.pluck(_.where(_$myTable.jqGrid("getGridParam").colModel, { edittype: 'checkbox' }), 'name');
if (checkboxNameSet.includes(cellname)) {
$('#' + rowid + '').addClass("edited");
}
}
})
Checkbox options are:
{
label: 'IsActive',
name: "isActive",
editable: true,
edittype: 'checkbox',
editoptions: { value: "true:false" },
editrules: { required: true },
formatter: "checkbox",
formatoptions: { disabled: false },
align: "center"
}
In addition, all the time, the network was fine.
Are there any options I missed or mistake?
Thank you for reading.