I concur with Capn Chuck, it's probably intermittent power connections.* My Raymarine ST6002+ unit began dropping out of auto and back into standby.* Turned out to be an intermittent ground connection.* Check the positive and negative connections to the computer.* Raymarine uses small set screws in a plastic mounting on the computer.* In my case the set screw for 12VDC negative had stripped the plastic housing so it was impossible to get a constant ground.* I ended up soldering in two pigtails, one for positive and one for negative.