@sgucuglu, everything you mentione din your post is hapenning to me. It started after an Update to iOS17.2 There were 2-3 versions before the last one, was working perfectly. In fact, the transparency mode was working even with iPhone 14 Pro max was off. I was so happy that I purchased a second pair. Like you mentioned the volume of Transparency mode is very low, even if it shows a check mark on the iPhone. Turning on and off goes back to normal.
I expected many more posts about this issue, but apperently not too many people are using the transparency mode as I am. Its a such a great feature, when I am shopping with my wife, I can hear her asking something and the music at the same time. I know some people are even using this mode when they are in the car. They say its much safer than to use the car radio. Because with this mode they can hear much better an upcoming emergency vehicle.
Calling tech support to find the solution did not help. And Senior advisor, did noteven have Airpods Pro himself to experiance an issue we are having.
So,lets hope that the new update will solve this problem.