I would recommend using data source + filter + listing web part to achieve this. Smart search was not built for this and searching is always bit non-deterministic. You need to keep in mind whether you want to filter the data or you are searching the data for something. Although it may look the same from the design point of view, there is a difference how it works in the backend, what code and logic is executed.
Or, if you want to stick with smart search, enable the query strings for filters - do not use the postback method for filters.