Maybe you thought it was some problems with your headphones as I thought and started a support ticket with Bose. But after hours of investigation I found out that the sound was unbalanced in the macOS – everything because a long lasting bug. It’s could happens when you press volume buttons when your Mac’s CPU is under heavy load.
A very annoying bug that should have been fixed long ago but I supposed it’s so few that really notice it and therefor no one really cares – sadly.
The solution I found was to install an app called Balance Lock that will help you keep your volume locked and balanced and if it drift away the app will correct it for you.