How stop iPhone lowering ringer volume
A restart of the ongoing problem since 2019:
The iPhone, over a few hours, on its own, lowers the ringtone volume to practically inaudible.
The suggestions from 2019, such as turning off "Change with Buttons" under "Sounds and Haptics", do not solve the problem. The iPhone has each OS update applied when released; no effect.
Any thoughts on when Apple may issue an update to remove the problem?
iPhone 13 Pro