@theengine could be an issue with your "gas gauge" circuitry on your circuit board but most likely it;'s your battery that is reporting "flaky" stuff. Start off by replacing the battery. If that does not fix it, you may have to start looking deeper into the circuitry of year headphones.
The battery is on the Left side. Remove the ear cushion. There you should find 4 screws. Two standard Philips and 2 Bose proprietary screws. You can use a rotary tool to drill those out or try a T5 security bit. Now you should have access to the battery.