Hi Oleg Ilin,
I was able to reproduce the issue as you do and this behavior is definitely is a bug and I have added a work item for this.
We will work to fix it as soon as we are able to!
I also would like to thank you for reporting this scenario as it helps us improve our products constantly!
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team
https://www.htmlelements.com/

Hi Oleg Ilin,
There is no new version available, yet. The latest Smart UI release is before you created this topic.
Best regards,
Peter Stoev
Smart UI Team
https://www.htmlelements.com/

Hi Oleg Ilin,

The fix for that item is scheduled for Q1 2022.

Best regards,
Peter Stoev

Smart UI Team
https://www.htmlelements.com/

Hi Oleg,

The reported issues are already resolved in the current version.

Example:

function GetData() {
    const data = new Array();
    const generatekey = function () {
        const S4 = function () {
            return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1);
        };
        return (S4() + S4() + "-" + S4() + "-" + S4() + "-" + S4() + "-" + S4() + S4() + S4());
    };
    for (let i = 0; i < 100; i++) {
        const row = {};
        const tasks = ["Shopping", "Housewares", "Kitchen supplies", "Groceries", "Cleaning supplies", "Office supplies", "Remodeling", "Paint bedroom", "Paint wall", "Fitness", "Decorate living room",
            "Fix lights", "Fix front door", "Clean kitchen"];
        const firstNames = [
            "Andrew", "Nancy", "Shelley", "Regina", "Yoshi", "Antoni", "Mayumi", "Ian", "Peter", "Lars", "Petra", "Martin", "Sven", "Elio", "Beate", "Cheryl", "Michael", "Guylene"
        ];
        const lastNames = [
            "Fuller", "Davolio", "Burke", "Murphy", "Nagase", "Saavedra", "Ohno", "Devling", "Wilson", "Peterson", "Winkler", "Bein", "Petersen", "Rossi", "Vileid", "Saylor", "Bjorn", "Nodier"
        ];
        const taskindex = Math.floor(Math.random() * tasks.length);
        row["id"] = generatekey();
        row["firstname"] = firstNames[Math.floor(Math.random() * firstNames.length)];
        row["lastname"] = lastNames[Math.floor(Math.random() * lastNames.length)];
        row["name"] = row["firstname"] + " " + row["lastname"];
        row["task"] = tasks[taskindex];
        row["duration"] = 1 + Math.floor(Math.random() * 10);
        data.push(row);
    }
    return data;
}
Smart('#grid', class {
    get properties() {
        return {
            dataSource: new Smart.DataAdapter({
                virtualDataSourceLength: 20,
                virtualDataSourceCache: true,
                virtualDataSourceOnExpand: function (resultCallbackFunction, details) {
                    setTimeout(function () {
                        const data = GetData().slice(0, 3);
                        if (details.row.level === 1) {
                            for (let i = 0; i < data.length; i++) {
                                data[i].leaf = true;
                            }
                            resultCallbackFunction({
                                dataSource: data
                            });
                        }
                        else {
                            resultCallbackFunction({
                                dataSource: data
                            });
                        }
                    }, 300);
                },
                virtualDataSource: function (resultCallbackFunction, details) {
                    setTimeout(function () {
                        resultCallbackFunction({
                            dataSource: GetData().slice(0, 20)
                        });
                    }, 300);
                },
                id: 'id',
                dataFields: [
                    'id: string',
                    'name: string',
                    'duration: number',
                    'task: string'
                ]
            }),
            layout: {
                rowHeight: 'auto',
                allowCellsWrap: true
            },
            behavior: { columnResizeMode: 'growAndShrink' },
            columns: [
                { label: 'Task', dataField: "task", align: 'center', width: 300 },
                { label: 'Person Name', dataField: "name", cellsAlign: 'center', align: 'center', width: 300 },
                {
                    label: 'Duration', dataField: "duration", cellsAlign: 'center', align: 'center', formatFunction: function (row, column, value) {
                        const hour = value > 1 ? " hours" : " hour";
                        return value + hour;
                    }
                }
            ]
        };
    }
});

Best regards,
Peter Stoev

Smart UI Team
https://www.htmlelements.com/