Hello,
i've digged around a lot, but there's a workaround: at this KB: https://kb.plesk.com/en/128801
{in short}
(make a backup) mysqldump -uadmin -p`cat /etc/psa/.psa.shadow` psa > psa_backup.sql
(connect to plesk db) plesk db
(search for site that use unity) select * from dom_param where...