Plesk error: "gzip: stdout: Broken pipe" when attempting to backup domains

Symptom

Full error during the backup is:

23:19:25 INFO Executing bundle producer: /bin/tar -C '/var/www/vhosts/domain.tld/statistics/webstat' -f - -c .
23:19:25 INFO Executing bundle producer: /bin/tar -C '/var/www/vhosts/domain.tld/httpdocs' -f - -c .
Can't use an undefined value as a symbol reference at Storage/Splitter.pm line 71.
23:19:25 INFO Executing bundle producer: /bin/tar -C '/var/www/vhosts/domain.tld/cgi-bin]' -f - -c .
gzip: stdout: Broken pipe
23:19:25 INFO Executing bundle producer: /bin/tar -C '/var/www/vhosts/revoit.com.hk/statistics/webstat-ssl' -f - -c .
23:19:25 ERROR Failed to create MIME messag

Cause

Backup utility failed to write data to disk for some reason.

Resolution

Check permissions on the backup folder and it's subfolders using the command below. The right permissions are shown on the second line:

grep DUMP_D /etc/psa/psa.conf | awk '{print "ls -ld "$2}' | sh
drwxr-x---  7 psaadm psaadm   /var/lib/psa/dumps