Each day MC is scheduled to update from an xml file. I tried that for a couple of days and have not seen entries missing. On the other hand, when I originally set it up, with no guide data to start with, I did see a few missing entries after the first couple of updates, regardless of the mode of operation (automatic background update, or manual update with GUI).
So, do you by any chance set up MC to clear all existing entries before loading new data daily?