Made the event store saves in the save monitor synchronous. Kevin Hoctor reported an issue where two save events arose with the same revision. This should not be possible, because save events are created atomically in a performBlockAndWait:. Except that the actual save was still being carried out asynchronously, and it is possible this could have led to a race condition.
Changed some NSAsserts in event fetching methods to error logging. They were throwing, and crashing the app.