Prevent friend's iOS devices from interfering with Bluetooth
This is happening with my new (2017) MacBook Air + wife's iPhone 8. She had a local account on the Air, signed into iCloud.

Signing her out of iCloud on the Air did not fix anything.

We removed the Air from her iCloud account via her phone, and all seems well now.

This was very annoying because my AirPods would start to have a "stadium" stereo effect every time her phone paired to the laptop.