I review an awful lot (some might say obsessively) on all sites I have the privileges to. At present, that's SO, ELL, RPG, SX, and Meta, spanning the gamut from "ridiculously super-busy" to "quiet beta site". Of those, I've noticed a surprisingly frequent glitch on only one of them, Meta.
/review shows that one of the queues has something in it… but if I check, there's nothing there (as the topbar indicator reflects), and if I check again a few minutes later, same, until at some point /review finally stops lying. This happens perhaps once or twice a week, and often for upwards of 15 minutes… sometimes an hour or more. Any queue can be affected, and once in a while, this happens for two queues at a time.
Now I suppose it might be "caching", but why isn't the topbar indicator (the usual culprit for silly caching bugs) affected, and why is Meta the only site with such bizarrely broken cache settings? And why does it cache a review entry when there isn't any?