Backoffice Upload Error

I have created a editor for file upload and used OOB ImpExExportResultDownload for file download.I have called both of these in backoffice editor area,but whenever I download file and then try to upload file,on selecting the file for upload error popup is shown saying "The server is temporarily out of service". Its giving 410 zk error in response header.I am using ZK File Upload component in my renderer. It works fine after refreshing,but issue comes if I click download and then try to upload.