Error trying to parse xhr response text in fineUploader file

Now I leave this wonderful version 3.3.0 to download and integrate all the libs into my website, I think that the downloads do the job fine, but no! I see an error in my javascript console:

[FineUploader] Sending upload request for 0

[FineUploader] xhr - server response received for 0

[FineUploader] responseText = 

and firebug with an error:

[FineUploader] Error when attempting to parse xhr response text (SyntaxError: JSON.parse: unexpected end of data)

on line error: jquery.fineuploader-3.3.0.min.js (line 148)

I am using params:

$(document).ready(function () {
    $('#uploader').fineUploader({
    request: {
        endpoint: '/upload/'
      },
    classes: {
        success: 'alert alert-success',
        fail: 'alert alert-error'
         }, 
    text: {
        uploadButton: '<i class="icon-upload icon-white"></i> file target'
      },
       validation: {
      sizeLimit: 31457280 

      },             
    debug: true

    });
  });

If I write sizeLimit: 10485760 - everything is in order, it works fine! download files to complete. If you write sizelimit: 31457280 the file does not load to the end, the process interruption up to 2 or 3%. Help me! where is the mistake? Please help me someone!