We often get posts from people with new DVRs worried that they will not record episodes because they do not appear in the to do list. It may sound illogical but these episodes WILL record. It can take a couple of weeks before episodes appear consistently in the to do list. Of course most people don't want to take the risk so they set the episodes manually.
Except when there is a guide data issue like 24, the Genies and DVRs are pretty well 100% reliable in their recordings. The situation where an episode records at a later date is also some sort of guide data issue.