This doesn't always happen but it has happened several times. If I'm not going to be able to watch CBS Sunday Morning live, I'll select it in the program guide to set a timer. I set the timer for DVR and once time event. Most weeks the program will record. Some weeks it doesn't. Today was a day when it didn't record. The timer was still in the timer list this evening when I discovered the failure. It appeared to be correct as to the program, the channel, the time, and the date.
Is there some reason this particular program wouldn't always record? I can't recall ever having a problem with any other program.