I, as well, have been seeing this issue quite frequently in the past few months with scheduled PQs. They never seem to run during the day they are supposed to and, if they come at all, it's sometime between 12-6 a.m. PT the next morning. This is very inconvenient when you are planning to make a caching trip the next day that starts early in the morning because you have to do all your prep before you leave the next day instead of the night before.
In my case today, however, the PQ I was waiting on (which I have set to run EVERY Monday and Friday), it never did run and I am currently sitting here waiting on it to be delivered, having even turned it on for Saturday now.
Very, very frustrating. I don't expect too much from my $30 membership, but having my PQs delivered is a big one!