To say that you have "Cascading ComboBox" functionality is misleading. You do have "Cascading ListBox" functionality - whereas if a value is picked in the parent listbox, the child will populate with a filtered, dependent list. Changing the parent changes the dependent items in the child list box.
However, the difference with ComboBoxes is that the user can also type a value in, if it doesn't appear in the bound dataset. While this does work as expected for the child ComboBox in the cascading example - it DOES NOT work for the parent. If you type a value into the parent, the child ComboBox remains disabled. You should be able to at least type into the child box.
We have a simple need for a Manufacturer / Model selection in two cascading ComboBoxes. If the manufacturer does not exist, we want to be able to allow the user to type it in. Since it's a new manufacturer - there are no associated models in the bound dataset, yet. The dependent child ComboBox should at least be enabled so the user can enter the new model.
This behavior can be experienced in your online example. If you pick a value in the parent, the child refreshes and rebinds accordingly. But if you type in the parent - the child remains disabled. This is a bug, if you intend on maintaining that you have "Cascading ComboBox" functionality.
I was given a "workaround" by your support team - but there are still lingering effects (especially on reloading the form with existing data) that would not be an issue if the cascading combobox implementation was completed properly.