On a TZ, after a few minutes of playing, the sounds with voice started getting garbled as shown in the first video. Sounds 14 - 21 have voice. But only 15 to 21 are garbled. Maybe this implied that the second ROM chip was bad. I sent the board for repair so it could be bench tested to ensure it would work. The repair person replaced all 3 ROM chips and changed out some capacitors.
The repair person tested the board for 10 hours using an MPU board I also sent for repair. He tested for 10 hours in test mode and it worked fine.
I received the board and tested in test mode for an hour and it worked fine.
The next day I went to play a game. As the last ball drained, I heard a pop sound and the sound became tinney as shown on the video below.
I ensured all chips are seated correctly. I ensured all ribbon cables and other connectors were in place. I replaced the ribbon cable between the MPU, Fliptronics, Sound, and display. I took each speaker out of the circuit one at a time. I removed the ribbon cable from the fliptronics board. I moved the ribbon cable from the display. I put the ribbon cable back and removed power to the fliptronics and then power to the display. I was using a different MPU so I put in the one that I sent in for repair so I was using the same MPU as he did.
The repair person is supposed to send another board to do a sanity check,
I did buy new Flipper Fidelity speakers but assume they will not make a difference until I solve the problem.
I have viewed all other Pre-DCS sound issues on pinside, I looked at the pinwiki and Clay's guides. I am not sure what to try next.