I have a Nokia 6 with Android 8.1.0 and a Bose QC35 II headset. It has recently started disconnecting frequently, from approximately every 10 seconds to every two minutes or so, seemingly getting more frequent over time. The batteries are both near full, and the headset is the only Bluetooth device paired with my phone.
So far I have tried
- restarting both devices,
- removing the pairing and re-pairing,
- toggling Bluetooth off and on again.
- clearing the Bluetooth app cache and storage and
- resetting all network settings in Settings - System - Reset options.
While typing this the device has reconnected at least five times. I was not transferring files or audio at the time. It happens in public and at home, where there are only two other Bluetooth-capable devices.
The sound is often choppy when it does work, so it's as if the signal is terrible even though the devices are less than a meter from each other.
When connected to my PC the sound is fine and the connection is stable for hours.
Edit: This no longer happens with Android, but I think it has something to do with the connection type. There is only one connection type which gives even close to reasonable sound quality, the other one crackles and spits and emits irregular "call from: [nothing]" garbage.