So when you find one that doesn't have a rating, just repeat yours or add a new one. That'll re-trigger the calculation. I'll work on a proper fix in a couple of days.
Sometimes when the database is overloaded, the calculation of overall ratings fails. All individual ratings are there but the average isn't calculated. It can be fixed by adding or modifying a rating.
So the missing album ratings are related to the slowdowns the site has been experiencing for a week and a half. I haven't had the time to investigate that properly.
