This is a very old import error.
Like around version 7.2.
But anyway to get people off of the mod groups needs a mysql query.
Then manually add the actual moderators back.
Try
https://www.ubbcentral.com/forums/ubbthreads.php/ubb/showflat/Number/223217/That will move the moderators to users.
Then just change the group id from 3 to 2 for global mods
Run again
Then manually add the actual moderators back.
But anyway to get people off of the mod groups needs a mysql query.
If you are leery then ask away for someone for hire or open a support ticket.
A far as deleting groups there was a bug that did not allow you to delete them the last time I tried.
But it will fail no matter what till you move the people out of those groups.
To move the people out of the custom groups just use member management.
Use the advanced search for selecting the custom groups
Then select all.
Then at the bottom are two options
select to change groups.
then elect all members in search.
submit and the next screen should be self explanatory.
As to add/move or delete
Meaning add to users
remove from the other custom groups.
