When I connect to my MacBook (macOS Mojave), I get no sound out of my left ear bud. When I go into my sound preferences, the "Output" tab shows the Bose Free SoundSport and indicates that the selected device has no output controls. This is the place where you usually see a balance control.
When you move to the "Input" tab, you can see that the Bose headphones are selected as an input device. When I de-select this and choose the "Internal Microphone", things change on the "Output" tab. Magically, now I have a Balance control for the output device and sound starts working for both ear buds.
THE BIG QUESTION - Is this a macOS or Bose issue? How do I avoid having to make this configuration change EVERY time I connect via bluetooth?