I think that somehow each Bluetooth device has its own kinks. With my QuietComfort 35 sometimes the A2DP profile is not negotiated and it falls back to HSP/HFP

I think that somehow each Bluetooth device has its own kinks. With my QuietComfort 35 sometimes the A2DP profile is not negotiated and it falls back to HSP/HFP which sounds like a landline in the 90s. Then you have to disconnect/reconnect it and hope it works this time. Another pair of cheap sports headphones I own just like to pair with everything that is in range if no other device is connected. And lastly my Sony WF-1000XM3 just never automatically connects to my phone. I always have to manually go into the Bluetooth menu to connect them. I think there should be some type of conformity certification, not for the implementation of the Bluetooth protocol itself but for how a device has to act in certain scenarios.