Many years back had a similar problem except in my case the PhD refused to shut down. There is a thread on Agon about this. It's a handshake problem and try a different interconnect between the phono and the TT.
Does anyone know that if the battery is starting to get week, does this effect the features of the preamp (not the quality of the sound but just some of the other functional features, in this case the sensitivity control of the unit, does this weaken and needs to be readjusted accordingly) I think that is the issue, now I have increased the gain of the sensitivity level and the problem is not fully gone but better, intermediate occurance only now. My question is, could this be an indication that the battery power is getting lower and very soon, the red LED will be showing up during play?
Thanks - R