Directv Control Box (DVR) giving problems

I have Directv.  The main control box (DVR box) has been giving trouble, and I believe I need to return it for replacement. There is something wrong with it. The problem is with recorded programs when playing back a recorded show. Unexpectedly, the playback just stops. This can last a few seconds or for much longer. Sometimes it starts up at the same point, other times at a point later in the playback probably equal to the time it was stopped (but no way to check). Sometimes the playback is fine for 10 minutes, then stops, then starts, then stops, then starts, multiple times in a very short span of time.  If you try to rewind past the point it stopped, sometimes you can, sometimes you can't.  Sometimes it just seizes up and you cannot even get out of playback mode.  Sometimes in this situation, even the "off" button is inoperative for a long time and you can't do anything.  (BTW the "unused space" is generally around 65% so it cannot be that the DVR is "too full".)  At other times, the picture itself in playback starts to breakup into streaks, or rectangular shapes, but then goes back to normal, often to repeat agin later.  Sometimes when I press "Off" on the remote, the TV goes off but the DVR back does not go off - the dark blue colored rings on the front of the box don't go completely out but change to a less intense color blue.

I have tried resetting the box multiple times over the course of this experience but nothing changes - same disfunction.  I called AT&T and spent more than an hour (nearly two) with a tech expert trying to run down the problem, resetting the box, all sorts of equipment tests.  The last time, it seemed to work at the end of 1-2 hours on the phone, but there is no way to be sure as it is unclear how long it takes for a playback to suddenly stop.  It seemed to function for a while but quickly went back after a few days to the point where it is was just as bad as before.  It is often nearly impossible to watch any recording with all these stop starts, unpredictable restarts, frequency f these, and so on.

I need to replace my DVR control box, or get it repaired, but cannot find out how to do so.  I will be happy to send it in, take it in, whatever, but just get me a box that allows me to watch without all these problems.

Thanks.