Symptoms
Picker auto insert value
Diagnoses
When you populate a picker control with data, the picker will also auto select a value and display it. By right, it should only populate the picker list.
Resolution
This has been logged this as a bug where the picker control will auto insert value in runtime. This will be fixed in a future release of the product. Which version, if any, this will be included in has not been determined at this time. Product Management makes these decisions based on criticality, customer demand, and other factors.
The workaround would be to use the "transfer data" rule to set the picker list and populated fields to empty whenever the picker value changes.