no confirmation when file upload

I am using VFB free version – 2.9.2 with Wp Version 4.4.5. I have discovered this problem where as when form is submitted with file uploaded there is no confirmation (page/text) and also no confirmation emails. Just blank page! Still form is received in VFB Entries section together with the file. The form results fine if logged in as the an admin. Also results are fine with out file upload.