SymptomsIn Parallels Plesk Panel 10.3, try to copy a website through Control Panel > Websites & Domains > Advanced Operations > Website Copying.
You will receive a message stating that the process started, but the process never finishes, and no files are copied.
ResolutionThe problem will be fixed in a future update of Parallels Plesk Panel that will be released after 10.3.1.
The Hotfix for 10.3 is attached. Extract file SiteCopyHelper.php from the attached archive and replace the existent file /usr/local/psa/admin/plib/api-common/SiteCopyHelper.php.