Tried to access a notification message (post approval request) as a board administrator, and got the following error message:
SQL ERROR [ mysqli ]
Duplicate entry 'post_in_queue' for key 'type' 
INSERT INTO op8_notification_types (notification_type_name, notification_type_enabled) VALUES ('post_in_queue', 1)
FILE: (not given by php)
LINE: (not given by php)
I was able to access it the first time, however I did something else for a minute (I think it was checking the user's credentials), and then came back and tried to access the notification again, when the error occurred.
May be related to this issue: