I have a wiki running MediaWiki 1.30 and PHP 7.0. On this site I have multiple groups with 2 of them being called staff and util in LocalSettings.php. I have allowed the util group technically to remove both the staff and util groups from any user but not add the groups. If I use createAndPromote.php to add a user into both groups and then try to add any other group to myself using Special:UserRights (bureaucrat for instance) it fails with this error The expiry time for group "staff" is invalid.
Please guide me in fixing this issue
Expected outcome: The group I want to add is added.
Current outcome: I get the error message above