DataGrid master detail hierarchy toggle arrows missing

I'm using DataGrid's hierarchy option as per the example on the demo page, but the rows can't be expanded. The first column with the small arrow used to switch details visibility is missing, and Grid.ExpandRows(Grid.PagedView) doesn't work. I set grid's ExpandMode="DataGridExpandMode.Single" and RowRender="GridRowRender". The event handler is as follows:

void GridRowRender(RowRenderEventArgs<Detail> args) {
    args.Expandable = true;

And the template is:

<Template Context="detail">
        <RadzenTabs TabPosition="TabPosition.Left" RenderMode="TabRenderMode.Client">
                <RadzenTabsItem Icon="info">
                <RadzenTabsItem Icon="functions">

I'll appreciate any help on this problem!

I noticed that the first column with the hierarchy (expansion) indicator (arrow) is there but it is 1-2px wide in my case. So now the question is why this column is so narrow and how to enlarge it?

Ok, found the reason why column is not visible - it's style was overridden intentionally. Now the problem/question is reversed. If ShowExpandColumn is set to false and the DataGrid doesn't have a Template, why in some cases the expandable indicator column is still visible?
That was the reason to hide this column through style.

<RadzenDataGrid TItem="Institution" Data="@Data" Count="@DataCount" LoadData="GetInstitutions" AllowSorting="true" AllowMultiColumnSorting="true"
                AllowColumnResize="true" AllowFiltering="false" @ref="Grid" @bind-Value=SelectedItems EditMode="DataGridEditMode.Single" ShowExpandColumn=false
                SelectionMode="DataGridSelectionMode.Single"  ShowMultiColumnSortingIndex="true"
                RowDoubleClick="@(args => EditGridRow(args))" IsLoading="@GridBusy" CellRender="@(args => GridCellRender(args, args.Data.IsValid))">

I'm unable to reproduce such behavior. Please provide complete code where this can be reproduced.

Sorry for the delay, but it was a mistake on my side. So ignore the last statement that the expandable indicator column stays visible