I have a Korg Pitchblack and sometimes I get "ghost readings". I'm not sure if this is what you mean... It's worst if the pick ups are too near or far from the strings. It will sort of register off key until the vibrations settle, then hold steady on the note.

Some things that help are setting up your pick ups, try switching pick ups, and finding the sweet spot oin the string. I think it creates a better harmonic. Depending what pick up, and where I pick the treble E string, for example, I can get almost no readable signal to the tuner. Move my pick 2 inches and get a perfect reading.

Sasme thing can happen with every tuner I have tried.

Maybe that'll help. :)