We just had this issue today, so we called them to figure it out. It was a big deal, since we don't watch live TV because our schedules don't allow us to be home when most of our shows come on.
Apparently, if you have too many recordings scheduled
in the next two weeks
(like, say, I don't know, three of the shows you record, including a 30-minute show, all have 24-hour marathons on top of your normal recordings), the system purges ALL
existing recordings. The number is 200 over a 2-week period, regardless of whether they are 15-minute shows (like several of ours are/were) or 1-hour shows or whatever.
I regularly go through and delete duplicates before they're even recorded (as soon as the titles appear), and, apparently, this isn't sufficient to prevent a problem.
Their basic reaction was that it was our fault.
I searched all over the Internet to see if I could find a similar bug mentioned for any other DVR system, and I couldn't. We never had the issue with Comcast, either. And, despite it being a known bug, I couldn't find it anywhere in their recommendations on how to use their DVR, either.
To put it another way: their DVR is a buggy piece of junk and they have no intention of fixing it. They're just hoping you won't notice.
We will probably drop UVerse after this.
P.S. Our deleted recordings included some that were "keep until I erase."