Iphone Turns Volume Down On Its Own

I recently purchased a "new" 1999 car for commuting. Of course, it does not have CarPlay or any sort of touch screen like my 2017 VW does. I purchased a bluetooth adapter so that I can play my audiobooks, music, and talk over the car radio. I use Apple Maps or Waze for Navigation.

On a frequent basis, I'll be driving and the volume will suddenly decrease. Of course, this is distracting and dangerous, because I wonder what is going on. While at a stoplight yesterday, I glanced at the Iphone and saw a message, stating "Volume Should be Turned Down" based on my last seven days of listening.

This is both annoying and dangerous, as I am distracted from driving while the volume suddenly and unexpectedly changes. I then have to turn it back up, taking my attention from the road.

I searched and found a thread from December on this bug: https://discussions.apple.com/thread/252118686

Has it been solved yet? I don't see a way to disable this. I am NOT listening on headphones, but rather through my car audio. I have the volume in the car at a comfortable level. The "headphone" volume is turned up to reduce distortion when playing through the car.

I have an Iphone 12 Pro Max.

TIA