Проблема с ComboBox MaterialDesign WPF

Почему такое происходит с ComboBox?

ComboBox comboBox = new ComboBox
{
   Margin = new Thickness(22, 7, 5, 0),
   VerticalAlignment = VerticalAlignment.Bottom,
   HorizontalAlignment = HorizontalAlignment.Stretch,
   VerticalContentAlignment = VerticalAlignment.Bottom,
   Height = 45,
   Style = (Style)FindResource("MaterialDesignFloatingHintComboBox")
};
comboBox.SetValue(HintAssist.HintProperty, Column);
comboBox.ItemsSource = db.Query<string>($"SELECT [{Columnn}] FROM [{Table}]").ToList();