Welcome to the Community,
unfortunately I'm not familiar with the Symantec Backup/Restore options. The first step to troubleshoot the issue would be to make sure that the conversion finished successfully, i.e. the process is not still accessing the .vmdk file(s). If you can confirm that the process completed successfully, please attach the VM's vmware.log file to a reply post to see whether this contains some hints on what to look for.
André