Carver Lighstar Direct Preamp

I have a Carver Lightstar Direct Preamp which has developed a problem. The volume cuts out on the right channel until you come to roughly every 3rd click on the remote control (it dosen't matter if you're decreasing or increasing volume) at which time the sound comes in at normal volume on both channels. (It does this right through all volume settings , from 0-63 on the preamp volume display). Does anybody know the problem and a possible fix? Thanks.