Apple TV audio is very loud in certain apps.
For example, when I navigate to the Disney+ app the volume is fine and adjustable. Once I select a movie to watch and begin watching, the volume in the movie is very loud and not adjustable. I try to lower the volume and it remains at the same loud volume until it's down to zero and then the volume is just off. Soon as you try to increase the volume again, it's back to loud. This happens in several apps but not all. Youtube, Netflix and my purchased movies have no issues. I have swapped out the HDMI cable and tried deleting and reloading an app. Apple TV software is up to date.