Full error message:

DBD::mysql::db do failed: Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation ‘=’
The system failed to lock the file “/home/username/etc/domain.tld/_privs.json” because of an error: Permission denied at /usr/local/cpanel/Cpanel/Transaction/File/Base.pm line 88.

Fix.
chown username.username /home/username/etc/domain.tld/