"Could not list files in destination" when backing up to a Windows FTP server

Symptoms

When attempting to validate a remote backup destination using Windows FTP Service, you may encounter errors such as this.

Error: Validation for transport “remote” failed: Could not list files in destination: Cpanel::Exception::InvalidParameter/(XID ap9ng2) “Cpanel::FileUtils::Permissions::String::str2oct” was given an invalid permissions string: 05-20-21

Description 

Validating remote backup locations uploads a test file, checks the ownership, permissions, and date of the file, and deletes the file to ensure that the connecting user can read and write to the disk on the remote server. Windows FTP Services have a different format than typical UNIX/Linux based FTP services, leading to the backup validation not being able to validate as the columns do not match expected output.

Workaround

Enabling MLSD or Unix directory listings within the Windows FTP Service which will allow the remote FTP validation to complete as expected.