Use attached to reproduce.

Workaround:
private void RadGridView1_ColumnChooserCreated(object sender, Telerik.WinControls.UI.ColumnChooserCreatedEventArgs e)
{
    var columnChooser = e.ColumnChooser as GridViewColumnChooser;
    columnChooser.Shown -= ColumnChooser_Shown;
    columnChooser.Shown += ColumnChooser_Shown;
  
}

private void ColumnChooser_Shown(object sender, EventArgs e)
{
    var columnChooser = sender as GridViewColumnChooser;
    var factor = this.FormElement.DpiScaleFactor;
    columnChooser.Scale(factor);
}