I have a form with a simple cascading dropdown situation. The first DataCard has a dropdown (Business Group) and the second DataCard has a combobox (Product Categories)
When a business group is selected if there are no product categories and the product categories box is clicked, the business group is reset. Also occasionally when there are product categories and one is selected the business group will reset.
Business Group
Item:
Filter(Sort('Business Units', Title, SortOrder.Ascending), Status.Value = "Active")
Default:
If(FormManageTitleQueue.Mode = FormMode.New, "", Parent.Default)
Product Categories
Items
Filter(Sort('Product Categories', 'Product Category', SortOrder.Ascending), 'Business Group'.Value = DropdownBusGroup.Selected.Title And Status.Value = "Active")
Default: Not set

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