The options are stored in the the search index property for each user and when the user clicks the button the chooses options from drop-downs are saved right?
I think you don’t need a property called last filter because you don’t need to save the results from drop downs and you can use the drop downs values in any screens to filter!
You can remove that last filter,filter and add the other filters as OR and try again ( you can use AND too to see the results that you get ).