I have the same problem.
In 7.2.2 , all my moderators can see a hidden board that only allows moderators/admins. They don't need to be the moderator of that hidden board.
After upgrading to 7.3.1 , moderators report that they cannot see that board . I thought maybe the permission changed. So I add every moderator to the moderator of that hidden board , BUT they still cannot enter that board. What happned ? What should I do now ?
Settings :
Forum Permissions : Can See Forum : Admin , GlobalModerators , Moderators .