Backup Manager shows the following warning while processing backup:
Encoding::encode: source UTF-8 encoding declared, but invalid UTF-8 sequence occured. Falling back to ISO-8859-1
Issue may be related to IDN domain name.
Files with non ASCII character file names in domain directory.
Make sure that there are no non ASCII characters in file names in domain directory at:
# cd /var/www/vhosts/example.com/httpdocs
# find . -type f | grep --color='auto' -P -n '[^\\x80-\\xFF]'
Rename files if any are found and try to backup once again.