DVR+ Not Keeping Accurate Time
 

My 7500 DVR+ clock is no longer maintaining accurate time frequently missing the beginning or recorded shows. I can set it for Auto Time, and it immediately jumps to 3 - 8 minutes behind the actual time. If I turn off Auto Time, then manually set it for the correct current time, it can within a couple of hours be behind by several minutes. I don't see a battery on the board, so a bad battery is not the issue. The unit is connected to the internet via Ethernet cable. Any suggestions on what could be causing this?