On further investigation, the Studio Console Log will display "Successful" for the import. The Windows event log will show no details of any error. You can launch Powershell from Studio and type the command:
Get-AppLibAppVpackage
This will display a list of the imported App-V packages. You may notice that there will be entries in there even though there is nothing in Studio. Notice the erroneous metadata entries (Your failed import attempts) and zero package GUID information. When you try to remove these entries using Remove-AppLibAppVPackage -UID, it will not work.
Citrix will implement a patch for this issue, but in the meantime, please be aware that if you add a package from any location that isn't a share, it will not display an error and it may create erroneuos metadata entries.