frostcrackle every hour or so, I'll get a notification when listening to music at high volume with "headphones" on (it's an aux cable plugged into my car).
What does the notification say, exactly? That info might help in understanding the problem.
pml One way I can think of disabling this is via adb.
This can be easily done in SystemUI Tuner
Using adb within the OS is discouraged, as explained here, and I think that would be a last resort – I'd personally argue it's not something that should be attempted at all – as the OP would be exposing their device to security risks.
Trusting a computer with ADB access within the OS […] exposes the device to a huge amount of attack surface and control by the trusted computer.