We use Html Report viewer for rendering reports based on Telerik Reporting.

We observe the following issue with report parameters with AvailableValues configured and Multivalue = true:

When there are one or more items from the available options selected - manually unselecting all of them leads to rendering a report as if the last unselected option is still selected leading to wrong result

 All other operations over the multivalue parameter work fine.

The issue occurs only in List type Parameter editors. With ComboBox editors this works as expected.