Random note sounded octave lower problem

[barlowstraker]

I bought a used Prologue 16 off of Reverb and it displays a bad problem. When in an Init Program patch it is easily heard in Poly mode. Whatever note you are playing over and over will randomly sound an octave lower (intermittently) and when that happens on that note the Oscilloscope shows a flat line. It is completely random but happens often (about every 6-8) notes played. Is this fixable without sending it in to repair? Really upset about this because other than that it is in perfect shape....