My TZ has had similar issues, re-seating the ribbon cables seemed to help, but I am not 100%, mine was doing the same thing (sounds being replaced with other sounds, kind of like some sort of default "well If i cant play this sound, I will grab this other one" behavior)
It happens so infrequently for me that I havent dug deeper (plus I am probably upgrading to a pinsound board)
Will be watching this to see what you end up doing with yours.