Backup manager fails to archive some of the files with the following warning:
PLESK_WARN: Warning: domain "sub.example.com" [4b4c9e3e-978c-4da3-9b5f-44d8a0b3666a]: Unable to get file attributes of C:\Inetpub\vhosts\example.com\\statistics\sub.example.com\very\long\path\verylongfilename.txt. File will not be archived [:86970428]
Name of the file (including path) is too long (more than 255 characters). It is a restriction of Windows operating system.
Shorten the path\name of the file and restart the backup.