SearchV2Async returning inconsistent results

given the following code:

namespace Dropbox
{
   internal class Program
   {
      static void Main(string[] args)
      {
         DropboxClientConfig config = new DropboxClientConfig
         {
            MaxRetriesOnError = 0
         };
         DropboxClient dropboxClient = new DropboxClient(AccessToken.ValidToken, config);

         SearchOptions searchOptions = new SearchOptions("", fileStatus: FileStatus.Active.Instance, filenameOnly: true, fileExtensions: new List<string> { "txt"});
         SearchV2Arg searchV2Arg = new SearchV2Arg("test", options: searchOptions);

         var result = dropboxClient.Files.SearchV2Async(searchV2Arg).Result;
         List<string> filePaths = new List<string>();

         foreach (SearchMatchV2 match in result.Matches)
         {
            filePaths.Add(match.Metadata.AsMetadata.Value.PathLower);
         }
      }
   }
}

if I run it, it shows the following results:

if I change the query value to "this" at line 19 and I run it, I get:

Note, the filePaths list is empty.  I would expect the two following file paths to be found (subset from the original 9 above):

"/this is a test.txt"

"/test 2/this is a test.txt"