3cd player doesn't play all songs.

My Koss home stereo has a 3 cd player.  Seems like the trouble started after I hit "random".  Now it only plays certain songs off of each cd no matter what cd I put in.  For example...Only the 2nd, 4th and 6th songs are played on each cd.  Am I stuck in random or a program installed by the previous owner to only play selected tracks?  Koss tells me they no longer make stereos, (of this type, that is), so a manual isn't available.  Need help getting out of wherever I am, please.