Based on the provided information I assume that the issue is that when the ListBox is bound to a dataSource (not initialized from already populated select element) all items are initially selected. Please correct me if I am wrong.
I have tested the described behavior in the following demo where the widget is bound to a remote data service and initially the items are not selected:
Could you please provide us with the steps to reproduce the behavior?
Having said that, sharing a demo that clearly replicates the issue would definitely help us fully understand the case and we will be able to provide further assistance to the best of our knowledge.
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