I have a Multivalue Report Parameter in the report that gets fed by a data source and may have more than 1000 selectable values. It is a ComboBox.

When I search and select a value from the dropdown, the selected value may not be passed with the reportSource of the viewer if I click directly the Preview button, without clicking outside the selection popup first. The issue occurs randomly. If I click outside the popup first, the values are passed correctly. I cannot reproduce the issue with less selectable items.