Add me to the list of people with MPU9211 sound issues. Mine is installed in a recently restored Sorcerer. I immediately noticed the difference in the background sounds (tinnier) and the voice sounded slightly distorted. I could live with that part of it.
Mine is on location so it gets a fair amount of play. Over the last couple of weeks, it has gotten worse. Now the attract mode speech and sound goes crazy with possessed sounding screeches and white noise sounds, or it will go through every callout like it is in test mode. Also, in game the sound will simply quit working. All of it. Then the machine has to be rebooted in order to get the sound back.

I emailed RD last week but never got a response.

I’m running several of the older RD boards in my FP and Flash without issue. And I received good support when I did have an issue with an original 937 board in the past. I’ll email him again next week.