Obligatory "but it works fine on my computer."

I have a grid with the last column being a dropdown from where you can select an option, and then OK. A coworker has discovered that when the area is clicked to reveal the dropdown, it resizes, causing all the data in the grid to shift to the left. Try as I might, I cannot replicate the issue, nor can I find any other problem relating to it, so that brings me here.

I received a video of the phenomenon, but here it is in gif form.

And here is the code used for this table.

                let columns = [
                    { headerText: "id", key: "id", dataType: "string", hidden: true },
                    { headerText: "No.", key: "項目No", dataType: "int", width: "60px" },
                    { headerText: "名前", key: "name", dataType: "string", width: "240px" },
                    { headerText: "<%=Session["shop_label"]%>", key: "store", dataType: "string", width: "240px" },
                    { headerText: "<%=Session["dept_label"]%>", key: "department", dataType: "string", width: "240px" },
                    { headerText: "権限", key: "roleId", dataType: "string", width: "240px", formatter: formatId },
                ];

                $("#grdMain").igGrid({
                    autoGenerateColumns: false,
                    renderCheckboxes: true,
                    width: "100%",
                    height: "500px",
                    rowEditable: false,
                    primaryKey: "id",
                    autoCommit: false,
                    columns: columns,
                    rowsRendered: function (evt, ui) { },
                    features: [
                        {
                            name: "Updating",
                            enableAddRow: false,
                            editMode: "row",
                            enableDeleteRow: false,
                            columnSettings: [
                                {
                                    columnKey: "id",
                                    readOnly: true
                                },
                                {
                                    columnKey: "項目No",
                                    readOnly: true,
                                },
                                {
                                    columnKey: "name",
                                    readOnly: true
                                },
                                {
                                    columnKey: "store",
                                    readOnly: true
                                },
                                {
                                    columnKey: "department",
                                    readOnly: true
                                },
                                {
                                    columnKey: "roleId",
                                    editorType: 'combo',
                                    required: false,
                                    editorOptions: {
                                        mode: "dropdown",
                                        dataSource: roles,
                                        textKey: "roleName",
                                        valueKey: "roleId"
                                    }
                                }
                            ],
                            rowEditDialogOptions: {
                                showReadonlyEditors: false
                            },
                            editCellStarting: function (evt, ui) {
                            },
                        },
                        {
                            name: "Sorting",
                            columnSettings: [
                                {
                                    columnKey: "項目No",
                                    allowSorting: true,
                                    currentSortDirection: "ascending"
                                },
                                {
                                    columnKey: "name",
                                    allowSorting: true,
                                },
                                {
                                    columnKey: "store",
                                    allowSorting: true,
                                },
                                {
                                    columnKey: "department",
                                    allowSorting: true,
                                },
                                {
                                    columnKey: "roleId",
                                    allowSorting: true,
                                    firstSortDirection: "descending",
                                },
                            ]
                        }
                    ]
                });

I'd like some insight for why this phenomenon happens and how I can fix it.