gunzip or tar x has nothing to do with creating archives.
You canīt write to the web-directory as long as the immutable-attribute is set for security-reasons. If you must create your backups in /var/www/clients/client1/web1, run
chattr -i /var/www/clients/client1/web1
create your backups
reset the attribute with chattr +i /var/www/clients/client1/web1
You can also disable this feature under serverconfig/web/Make web folders immutable.