DVR Recording ending before show ends

One known challenge with DVR which is extremely difficult to overcome is that each network as well as the box itself keep time differently.  While it usually doesn't vary by much a minute two here and there will cause what you're seeing.  The box does have a feature to try and mitigate this issue by allowing you to set it to record additional time at the start or finish of a recording.  When setting a scheduled recording you should see options for configuring this.