Much of the precinct level results files for Washington seem to be aggregated from the counties and don't follow a consistent format. Also, many of the results are spread between multiple worksheets in the Excel files and it will take some time to figure out how to navigate the different sheets or to review the data to determine which sheet(s) to use.

Some of these files are listed in openelex.us.wa.load.LoadResults.bad_filenames (source, but I believe there are also others that can be found when the loader outputs a warning about not loading any results (though its also possible that, for some elections, there aren't statewide or federal races for some counties).