dvr shows disappearing

Hello,

My DVR is recording shows based on the settings I have made, but all disappear in the middle of the night. Last night I watched recorded shows until about 10 PM. The only shows to watch were recorded yesterday, nothing older was in the dvr all gone. When I checked at 6am today, only shows recorded after midnight were there, not the ones from last night that I didn't watch. Whats going on?