I believe the exception occurs because you're trying to add a controlee to a session that already has a controlee. You've specified the device in the peerDevices property, so when the session starts, the controlee is already configured. There is no need to call addControlee() afterwards.

I previously implemented an app for ranging between an Android phone and the Qorvo DWM3001CDK board, but the app can also be used for ranging between two Android phones. When I modified my app to be similar to your code, I encountered the same error. However, when I removed the addControlee() call, I was able to perform ranging with the Qorvo board.

Also note that the UWB address of a phone is random and changes with every session. Therefore, I recommend splitting the controllerSessionScope() call into a separate function and using the localAddress property to obtain the random address. You can then input this address on the other device (and vice versa) before starting the ranging session, you can check the source of my app for details.