I have a new 722 as of September and mine is doing fine. Sometimes shows run over or start late.... that's why the gods made TV Guide I guess.
If you changed the timing on one show, the 722 then asks if you want that 'timer'/timing event to cover only that show or all shows. Could it be that you changed one show, chose to to have it cover all shows and now all are cutting off the end? Or could it be the internal clock gets messed up - I haven't figured out just how that is set?
I noted that if you choose to record two programs back-to-back that are on the same channel then the unit automatically sets the end to be at '0' and also the start to be at '0' from the GUIDE's idea of when a show starts and stops (that doesn't work if they are on different channels). I've noticed that is sometimes about 15 seconds before what I know to be the top of an hour. But some shows are now having content run to that last possible moment in their time-slot and sometimes I get the end on the beginning of the next show.
As to a show that is not followed by a another recording event, I always use the 'Option' menu (I think that is it) after I create the timer to adjust the start and end times and make that ending time is about 2-3 minutes later than stated end time. So if a show ends at 5 minutes after the hour, I set the timer to end 7 or 8 minutes later than what DISH's Guide would record. I don't trust the Guide most times, and so far, I haven't missed anything.